Amid rising tensions between North Korea and the US, Pyongyang has detained a US citizen, officials said on Sunday, bringing to three the number of Americans now being held in the country.

As two Japanese navy ships joined a US carrier group for exercises in the western Pacific, North Korea threatened to sink a US aircraft carrier.

“Our revolutionary forces are combat-ready to sink a US nuclear-powered aircraft carrier with a single strike,” the Rodong Sinmun, the newspaper of the North’s ruling Workers’ party, said in a commentary.

The paper likened the aircraft carrier to a “gross animal” and said a strike on it would be “an actual example to show our military’s force”. The commentary was carried on page three of the newspaper, after a two-page feature about the country’s leader, Kim Jong-un, inspecting a pig farm.

Donald Trump ordered the USS Carl Vinson carrier strike group to sail to waters off the Korean peninsula in response to rising tension over the North’s nuclear and missile tests, and its threats to attack the US and its Asian allies.

The US has not specified where the carrier strike group is. The vice-president, Mike Pence, who recently visited South Korea on a Pacific tour, said on Saturday the ships would arrive “within days” but gave no other details.

North Korea has also threatened Australia, where Pence was on Saturday and Sunday, with a nuclear strike if it continues “blindly and zealously toeing the US line”.

Speaking on a visit to Greece, the Chinese foreign minister, Wang Yi, appealed for calm. “We need to issue peaceful and rational sounds,” he said, according to a statement issued by China’s foreign ministry.

Trump was scheduled to speak to President Xi Jinping of China and Prime Minister Shinzo Abe of Japan later on Sunday, a White House official told Reuters.

The official also said the White House was expected to host senators for a briefing on North Korea on Wednesday. The official said the briefing would be led by the secretary of state, Rex Tillerson; the defense secretary, Jim Mattis; the director of national intelligence, Dan Coats, and the Marine general Joseph Dunford, chairman of the Joint Chiefs of Staff.

The detained American, according to Park Chan-mo, the chancellor of the Pyongyang University of Science and Technology, is Tony Kim, who also goes by his Korean name, Kim Sang-duk.

Park said Kim, who is in his 50s, had taught accounting at the university for about a month. He said Kim was detained by officials as he was trying to leave the country from Pyongyang’s international airport.

The Swedish embassy in Pyongyang said it was aware of a Korean American citizen being detained recently, but could not comment further. The embassy looks after consular affairs for the US in North Korea because the two countries do not have diplomatic relations.

Park said Kim had taught at the Yanbian University of Science and Technology in China before coming to Pyongyang. He said he was informed that the detention had “nothing to do” with Kim’s work at the university but did not know further details.

As of Sunday night in Pyongyang, North Korea’s official media had not reported on the detention.

Though no details on why Kim was detained have been released, the detention comes at a time of unusually heightened tensions between the US and North Korea. Both countries have recently been trading threats of war and having another American in jail will probably up the ante even further.

Last year, Otto Warmbier, then a 21-year-old University of Virginia student from suburban Cincinnati, was sentenced to 15 years of hard labor in prison after he confessed to trying to steal a propaganda banner.

Kim Dong Chul, who was born in South Korea but is also believed to have US citizenship, is serving a sentence of 10 years for espionage.

Another foreigner, a Canadian pastor, is also being detained. Hyeon Soo Lim, a South Korean-born Canadian citizen in his 60s, was convicted and sentenced to life in prison in 2015 on charges of trying to use religion to destroy the North Korean system and helping US and South Korean authorities lure and abduct North Korean citizens.