China's President Xi Jinping has called for restraint when dealing with North Koreaduring a telephone call with President Donald Trump, according to Chinese state media.
The official broadcaster CCTV quoted Xi on Monday as telling Trump that Chinastrongly opposed North Korea's nuclear weapons programme, which are in violation of UN Council resolutions, and hoped "all parties will exercise restraint and avoid aggravating the situation" on the Korean Peninsula.
The Trump administration has warned that all options, including a military strike, are "on the table" to halt North Korea's ambitions of developing a nuclear-tipped missile that could reach the US mainland.
The phone call, which took place on Monday morning Beijing time, came amid speculation that North Korea could hold a sixth nuclear test this week.
North Korea often marks significant dates by displaying military capability, and South Korean officials say there is a chance the country will conduct a nuclear test or a major missile launch around the founding anniversary of its military on Tuesday.
On April 15, North Korea showed off its advancing nuclear weapons and missiles programme in a massive military parade in Pyongyang honouring late state founder Kim Il-sung, the grandfather of the current ruler.
The displayed military hardware included prototype ICBMs and new midrange solid-fuel missiles that can be fired from land mobile launchers and submarines, making them harder to detect before launch.
Trump has pressed Xi to exert greater pressure against North Korea, given China's status as the country's sole economic lifeline and major ally. Monday's call is the second time that the two leaders have spoken by telephone since meeting in Florida earlier this month.
Trump also spoke Monday with and Japanese Prime Minister Shinzo Abe, and they agreed to urge North Korea to refrain from what Abe called provocative actions.
Speaking in Sydney on Saturday, US Vice President Mike Pence said the American aircraft carrier USSCarl Vinson would arrive in the Sea of Japan, bordering the Korean Peninsula, "in a matter of days".
The ship joined other warships for joint exercises with Japan in the Philippine Sea on Sunday.
Confusion has clouded the carrier group's whereabouts in recent days after President Donald Trump suggested the "armada" was steaming towards North Korea when in fact it was sent towards Australia.
US citizen named
The US citizen detained by North Korea on Saturday has been named as Tony Kim, who also goes by his Korean name Kim Sang-duk.
Kim, who is 58, taught accounting at the Pyongyang University of Science and Technology for about a month, according to the university's chancellor Park Chan-mo.
Park said Kim was detained by officials as he was trying to leave the country from Pyongyang's international airport. A university spokesman said he was trying to leave with his wife on a flight to China.
The detention brings the total number of Americans now being held in North Korea to three.
Against this backdrop of tensions on the peninsula, the issue of North Korean refugees in Chinese detention was raised on Monday by Human Rights Watch.
China should immediately reveal the whereabouts of eight North Koreans it detained last month, the US-based rights organisation said.
It said they risk severe torture if they were returned to the North.
Most North Korean refugees begin their escape by crossing into China and then try to make it to third countries - often in Southeast Asia - where they seek asylum in the South.
If caught and returned to the North they can face severe punishment.
China regularly labels North Koreans as illegal "economic migrants" and repatriates them based on a border protocol adopted in 1986.
"By now, there are plenty of survivor accounts that reveal Kim Jong-un's administration is routinely persecuting those who are forced back to North Korea," said Phil Robertson, deputy Asia director for Human Rights Watch.
"There is no way to sugar coat this: if this group is forced back to North Korea, their lives and safety will be at risk," Robertson said.
More than 40 North Koreans, including children and pregnant women, have been held by China over the past nine months, Human Rights Watch said, and at least nine forcibly returned to the North.
Since the end of the Korean War in 1953, more than 30,000 North Koreans have escaped - most after a deadly famine in the mid-90s - and settled in the South.
North Korean leader Kim Jong-un is believed to have tightened border controls since he came to power after the death of his father Kim Jong-il in December 2011.
The number of refugees arriving in South Korea plunged nearly 50 percent to 1,417 last year.