BEIJING (REUTERS) - Chinese police "took away" a well-known columnist last week before he tried to board a flight for Hong Kong and his whereabouts are still unknown, his lawyer said on Monday (March 21).

Jia Jia, who writes a regular column for Tencent Online, went missing late on March 15, around the time he was scheduled to board a flight from Beijing to Hong Kong.

He had warned former colleagues of the danger of re-publishing an open letter calling for President Xi Jinping to resign.

"We only know that on that day, March 15, Beijing public security bureau officials went to the airport to take Jia Jia away. Airport officials also assisted them. This is based on a notice from the airport officials," lawyer Yan Xin told Reuters. "Since then, there is no new development, we haven't received any more communication. As for the events that followed and whether it was a detention, we're still unsure." Calls seeking comment from the Beijing police and airport officials went unanswered.

A spokesman for China's Foreign Ministry, the only government department to hold a daily news briefing for foreign reporters, said her ministry was not the right one to direct a question to.

"Lots of things happen in China every day," spokesman Hua Chunying told a briefing. "There are lots of things worth reporting in China, and you should not focus so much on individual cases."

President Xi Jinping has embarked on an unprecedented effort to clamp down on the Internet and censor opinions that do not reflect those of Communist Party leaders, including by imposing tougher penalties for "spreading rumours" via social media.

An online letter, which circulated widely at the start of China's parliament this month and was signed by "a loyal Communist Party Member", had called for the immediate resignation of Xi and blamed him for "unprecedented problems".

Last week, Yan told Reuters that Jia Jia had told friends before boarding the flight to Hong Kong that he had no connection to the letter.

Jia Jia's case has attracted international concern from rights groups such as Amnesty International.

On Monday, an editorial in the state-run tabloid The Global Times criticised the international community for going "against the Chinese government" and jumping to conclusions before authorities announced findings. "Any suspicions about 'custody or arrest in secret' are ill-founded," it said in an editorial.

The paper said that while family members should be notified within 24 hours if someone was detained, that timeframe could be extended if it involved "national security".