A U.S. fast-attack, nuclear-powered submarine struck a mystery object while submerged in international waters in the Indo-Pacific region, the U.S. Pacific Fleet said on Thursday, injuring as many as 11 sailors.
In a brief statement, the Navy said the U.S.S. Connecticut remained in a stable condition and that her nuclear plant was not damaged.
It did not offer a specific location but U.S.N.I. News reported that it happened in the South China Sea.
A defense official told the site that 11 people were injured and the boat was now headed to Guam, where it was expected to arrive on Saturday.
The region has been the scene of intense naval activity in recent years as China flexes its military muscles and the U.S. conducts 'freedom of navigation' missions to limit Beijing's influence.
The accident comes as Washington expresses concern about China's increasingly belligerent stance towards the self-governing island Taiwan.
And on Thursday it emerged that U.S. special forces and Marines have been training troops on the South China Sea island for at least a year.
In a statement, the Pacific Fleet said the Seawolf-class fast-attack submarine USS Connecticut struck an 'unknown object' on Sunday.
'The safety of the crew remains the Navy’s top priority. There are no life threatening injuries,' it said.
'The submarine remains in a safe and stable condition.
'USS Connecticut’s nuclear propulsion plant and spaces were not affected and remain fully operational.
'The extent of damage to the remainder of the submarine is being assessed. The U.S. Navy has not requested assistance. The incident will be investigated.' The 353-foot boat was commissioned in 1998 and sails with a crew of 116, including 15 officers.
It can carry 40 torpedoes or missiles.
Officials offered no further details about its activities in the region. But its presence in such a sensitive location will spark speculation about what could have caused the accident.
Earlier the Central Intelligence Agency announced a reorganization on Thursday, putting a greater focus on China as tensions continue to rise between the world's biggest economies.
The CIA's new 'China Mission Center' was unveiled as a report claimed that U.S. special operations forces and Marines had been secretly operating in Taiwan to train military forces there for the past year.
Increasing tensions in the South Sea China have triggered warnings of war after sent air sorties and hostile rhetoric towards the self-governing island.
CIA Director William Burns said the new unit was a result of strategic reviews that concentrated on 'China, technology, people, and partnerships.'
'CMC will further strengthen the agency's work on the most important geopolitical threat we face in the 21st century, an increasingly adversarial Chinese government,' he said.
The reorganization marks an indication of how the Biden administration is reorienting to face the threat from China.
And it comes amid growing concerns in particular about Taiwan and Beijing's threatening moves.
About two dozen members of U.S. special-operations and support troops are training small units of Taiwan’s ground forces, officials told the Wall Street Journal, while Marine are working with local maritime forces.
They said the forces had been operating there for at least a year.
A Pentagon spokesperson declined to comment on the report directly.
'I would note, the PRC has stepped up efforts to intimidate and pressure Taiwan and other allies and partners, including increasing military activities conducted in the vicinity of Taiwan, East China Sea, and South China Sea which we believe are destabilizing and increase the risk of miscalculation,' said John Supple.
'I don’t have any comments on specific operations, engagements, or training, but I would like to highlight that our support for and defense relationship with Taiwan remains aligned against the current threat posed by the People’s Republic of China.
'We urge Beijing to honor its commitment to the peaceful resolution of cross-Strait differences, as delineated in the three communiques.'
The U.S. has sold billions of dollars in weapons to Taiwan despite a policy of 'strategic ambiguity' over whether the U.S. would defend the island from a Chinese invasion.
But officials believe Taiwan must do more to counter the growing jeopardy it faces.
On Wednesday, America's top diplomat to the island said China posed a 'real and immediate' danger.
James Moriarty, speaking Wednesday night at an event to mark Taiwan's National Day in Washington, said China's recent show-of-strength in the skies near the island are a reminder of the threat it faces.
Moriarty, who heads the American Institute in Taiwan which represents the US on the island, said the incursions underlined the need for the ruling Republic of China to establish 'a powerful intimidating [defence] force as soon as possible.'
China flew some 150 aircraft into Taiwan's 'air defence zone' over the weekend in one of the largest displays of force in recent years.
The missions had caused international alarm, Moriarty added, showing that the world is now paying attention to Taiwan and is ready to lend support.
Underlining his point, delegations of Australian and French diplomats visited the island on Thursday - holding high-level meetings with President Tsai Ing-wen.
Alain Richard, head of the French mission and a former defence minister, referred to Taiwan as 'a country' during as he was awarded the Order of Propitious Clouds for helping to establish diplomatic ties.
The remark is sure to infuriate Beijing, which views Taiwan as a breakaway province.
Officially, it is not recognised as a country under international law, though the government considers it to be an independent state.
The Chinese embassy in Paris warned that Richard's visit will damage the interests of China, Chinese-French relations and 'the image of France'.
Meanwhile former Australian Prime Minister Tony Abbot was also on the island today, also in an effort to improve relations and 'end the isolation from which Taiwan has been suffering for so many decades.'
'Over the past 70 years, Taiwan has transformed from an impoverished dictatorship into a vibrant, dynamic, pluralist democracy,' he said as he arrived.
'You have demonstrated to all the countries of this region that it is possible to be rich and free.'
It is not clear if Mr Abbot will meet with the French mission while he is on the island.
Australia's relations with France are currently strained after Canberra ripped up a billion-dollar contract to buy French submarines and signed a new deal with the UK and US to acquire nuclear ones - dubbed AUKUS.
The move infuriated Beijing, which warned it risked stability in the region by upsetting the balance of power.
Western nations have been rushing to reaffirm their support for Taiwan as it faces down threats from an increasingly-assertive China.
Tensions have been building ever since a 2019 speech by President Xi Jinping in which he vowed to 'reunify' Taiwan with mainland China - using force if necessary.
He spoke against the backdrop of a rapid expansion of China's military, including the construction of new bases in the South China Sea - where Taiwan is located and over which Beijing claim supreme authority.
That has prompted the US - a long-standing ally of Taiwan - to forge new alliances in the region to counter-balance the growing threat.
As well as the AUKUS pact, Biden has entered into a strategic partnership known as The Quad with India, Japan and Australia to share intelligence and carry out joint military drills in the region.
In a huge show of force to Beijing, the US is also participating in huge naval exercises in the region led by Britain's newest aircraft carrier - HMS Queen Elizabeth.
'Big Lizzie', as she is affectionately known, is currently leading drills with a joint carrier strike group that includes the USS Carl Vinson and USS Ronald Reagan, along with ships from New Zealand, the Netherlands, Canada and Japan.
The carriers and their escorts have been carrying out drills in the South China Sea, and are expected to arrive in Singapore shortly.
Taiwanese president Tsai Ing-wen on Tuesday vowed to 'do whatever it takes' to guard Taiwan against invasion as she indicated that without help from the country's allies 'authoritarianism has the upper hand over democracy.'
Tsai added: '[Democratic nations] should remember that if Taiwan were to fall, the consequences would be catastrophic for regional peace and the democratic system.
'It would signal that in today's global contest of values, authoritarianism has the upper hand over democracy.'
Taiwan hopes for peaceful coexistence with China, she said, but 'if its democracy and way of life are threatened, Taiwan will do whatever it takes to defend itself.'
Tsai's government on Monday urged Beijing to stop 'irresponsible provocative actions' after the warplanes breached Taiwan's air defence identification zone (ADIZ).
'Amid almost daily intrusions by the People's Liberation Army, our position on cross-strait relations remains constant: Taiwan will not bend to pressure,' Tsai added.