Rights groups have condemned China after a Beijing-based journalist went missing, linking his disappearance to an unusual open letter calling for President Xi Jinping's resignation.

Jia Jia, a freelance journalist, has not been seen since Tuesday, his lawyer told AFP, without giving further details.

Amnesty International said a close friend of Jia told the group he disappeared some time after going through customs at Beijing airport when about to board a flight to Hong Kong.

"He went missing on the 15th," lawyer Yan Xin said, citing the journalist's wife.

City University of Hong Kong also confirmed to AFP that Jia had not turned up to a seminar he was due to give on Thursday.

"We are deeply concerned by Chinese journalist Jia Jia's disappearance," said Bob Dietz, Asia program coordinator for the Committee to Protect Journalists.

"If he is in police custody, officials must disclose where they are holding him and why. If anyone else knows where he is, they should step forward and clarify this worrisome mystery."

Under Xi, China's ruling Communist Party has tightened controls over civil society, detaining or interrogating more than 200 human rights lawyers and activists last year in what analysts have called one of the biggest crackdowns on dissent in recent times.

Sophie Richardson, China director for Human Rights Watch, voiced concern over Jia on Twitter.

"#China disapps journo--no longer enough to just erase all trace of criticism. Trend now is to erase critics, too," she tweeted.

Both Amnesty and the CPJ have linked Jia's disappearance to an open letter published on the news website Wujie News earlier this month calling for Xi's resignation.

The letter, which was rapidly removed, was signed "Loyal Communist Party members", but little else is known about its authorship.

"His going missing is most likely related to the publishing of the letter and perhaps the authorities' implication of his involvement or knowledge of the letter," Amnesty China researcher William Nee told AFP.

"Journalists and activists are forced all the time to 'drink tea' with the authorities... but it generally doesn't last this long," he said, adding that officials usually try to extract information during such meetings.

However, Jia's lawyer Yan said his disappearance may not be connected to the letter.

China is currently in the spotlight over the disappearances last year of five Hong Kong booksellers who reappeared on the mainland, as well as the use of televised confessions from suspects.

The five booksellers were from Hong Kong's Mighty Current publishing house, known for its salacious titles critical of Beijing.

Starwood Hotels dumps Marriott for raised Chinese bid
New York (AFP) March 18, 2016 - Starwood Hotels said Friday that it favors a takeover bid from a consortium led by China's Anbang Insurance over an earlier deal with Marriott, after the Anbang group increased its offer.

Starwood's board was persuaded by Anbang's $2 increase in its Monday offer to $78 a share, and said it plans to notify Marriott International that their already agreed merger was off.

Starwood had agreed to Marriott's $63.74 per share cash-and-stock offer last November for its network of 1,270 properties in 100 countries, including the Westin, Sheraton, Le Meridien and W brands.

But the Chinese giant stepped in the way this week as it announced nearly $20 billion in two proposed hotel takeover deals.

The Anbang proposal values Starwood at $13.2 billion and comes as the Chinese giant has also agreed to buy a portfolio of 16 luxury hotel and resort properties from the Blackstone group for $6.5 billion.

With the new Anbang offer, Starwood's board said in a statement that it "intends to terminate the Marriott merger agreement and enter into a definitive agreement with the consortium."

The news pushed Starwood shares up 4.5 percent to $79.91 in early trade. Shares of Marriott, which will earn a $400 million fee for Starwood cancelling their deal, rose 2.0 percent to $73.23. Anbang is privately controlled.

Anbang's partners in the deal include China-based Primavera Capital and US private equity investor JC Flowers & Co.

Anbang first pushed into the US hospitality industry in October 2014 by acquiring the famous Waldorf Astoria Hotel in Manhattan for nearly $2 billion from Hilton Worldwide Holdings.

The purchases are part of an aggressive international push by the 12-year-old insurer, which reports assets of 1.65 trillion yuan ($254 billion), more than 3,000 branches in China and over 30,000 employees globally.

In November, Anbang bought US insurer Fidelity & Guaranty Life for $1.6 billion, after snapping up Korean insurer Tong Yang Life for around $950 million and Dutch insurer Vivat for about $167 million earlier in the year.