China has for the first time allowed three North Korean defectors to seek asylum in the United States, South Korean newspapers said Tuesday.

The three left for the United States on Saturday, the Chosun daily and other newspapers said. They were among four North Korean refugees who broke into a US consulate in the northeastern Chinese city of Shenyang in May.

The fourth refugee, who had worked for a North Korean security organization, is still staying in the US mission, Yonhap news agency said.

It marked the first time China had allowed North Korean defectors to seek asylum in the United States, Yonhap said.

US and South Korean officials refused to comment on the report. "We never talk about refugee cases," a spokeswoman at the US embassy in Beijing said.

Beijing had usually allowed North Korean defectors in high-profile cases to seek asylum in other countries, mostly in South Korea. But this was only after they were first sent to third-party countries.

Six North Korean defectors staying in a Southeast Asian country were granted asylum in the United States in May, under the US's 2004 North Korean Human Rights Act.

Human rights groups say up to 300,000 North Koreans have fled to neighbouring China. Many seek passage to South Korea, usually by travelling via a third country but sometimes by taking refuge in embassies in Beijing.

China treats North Koreans as illegal immigrants and has an agreement with their government to deport those it catches.

About 1,390 North Korean defectors arrived in South Korea last year, bringing the number since the 1950-53 Korean War to 8,000.

But activists complain South Korea is now cautious in accepting North Korean defectors in an effort to boost inter-Korean rapprochement.