BEIJING (AFP) -- Chinese President Xi Jinping suggested US news organisations had themselves to blame for Beijing not granting journalist visas, in response to a rare unscripted question from a foreign reporter on Wednesday.

Washington has criticised China's treatment of foreign correspondents after reporters from The New York Times and Bloomberg were not given residence visas in apparent retaliation for investigative stories on the wealth amassed by leaders' families.

Beijing is highly sensitive about critical coverage of its leaders, while also keeping a tight grip on information in the country.

Xi's joint press conference with US President Barack Obama was not carried live by China's state broadcaster CCTV or other mainland channels.

Xi hardly ever takes questions in public, and queries at the premier's once-a-year press conference after the annual meeting of China's parliament are always discussed in advance.

But the White House insisted that questions should be allowed at the Great Hall of the People event, and one from each side was authorised.

The American question went to the New York Times, which published an investigation in 2012 into the family wealth of then premier Wen Jiabao. That year, Bloomberg news agency did the same regarding Xi's relatives, and ever since Beijing has blocked the websites of both outlets, while new journalists working for them have not been granted visas.

This week the US and China agreed a reciprocal deal to extend the validities of tourist, business and student visas and the reporter asked -- among other topics -- "Isn't it time to extend that sort of right to foreign correspondents who seek to cover your country?"

Xi at first appeared to ignore the reporter's questions entirely. When it was his turn to speak after Obama, he instead asked the assembled Chinese journalists to offer a question.

At the end of the event, however, he returned to the topic and issued a stern warning that "media outlets need to obey China's laws and regulations".

"When a car breaks down on the road, perhaps we need to get off the car to see where the problem lies," Xi said. "And when a certain issue is raised as a problem, there must be a reason."

"In Chinese, we have a saying: 'The party which has created the problem should be the one to help resolve it'. So perhaps we should look into the problem to see where the cause lies," he added.

The remarks are the most direct by a Chinese leader on the issue to date.

Over the past two years, three Times journalists have been denied authorisation to stay in China, a development that the Foreign Correspondents' Club of China in January criticised as falling "well short of international standards".

"In these circumstances it is difficult to avoid the conclusion that the authorities are punishing the New York Times for articles it published concerning Premier Wen Jiabao and his family," the group said in a statement at the time.