Minnie Chan, a senior reporter covering security matters at the newspaper, travelled from Hong Kong to Beijing to report on a Chinese defence forum on Oct. 29-31, according to two sources close to her.

Four sources familiar with the matter, including SCMP colleagues of Chan and her friends, say they have not been able to contact her since the day following the forum. The sources declined to be named due to the sensitivity of the situation.

"The Hong Kong Journalists Association is deeply concerned for Minnie's safety and is requesting more information from the SCMP," said the group in a statement.

SCMP told Reuters that Chan has "taken personal leave." It added that Chan's family "informed us that she is in Beijing but needs time to handle a private matter. Her family has told us she is safe but has requested that we respect her privacy."

The newspaper said, "the safety of our journalists in the course of their professional work is of the utmost importance," and that it would "continue to communicate with Minnie's family and provide all the necessary support they need."

China's Foreign Ministry spokesman Wang Wenbin said he "didn't know about the relevant situation," when asked about Chan's case at a regular media briefing.

Hong Kong's Security Bureau had no immediate comment.

The SCMP is owned by Chinese technology giant Alibaba Group.

Kyodo News first reported the news of Chan being unreachable.

Reuters was not able to determine Chan's current whereabouts. Calls, WeChat and WhatsApp messages to her mobile phone went unanswered. Reuters was unable to reach any relatives of Chan for comment.

A fellow reporter who travelled with Chan to Beijing for the forum had returned to Hong Kong after the event and has since published articles, one of the sources said.

Two staffers at the SCMP said Chan's name had been on the work roster for part of November.

The Xiangshan Forum covered by Chan is China's biggest annual show of military diplomacy. It was held at a sensitive time for Beijing soon after it sacked former defence minister Li Shangfu who is yet to be replaced.

(Reporting by Hong Kong and Beijing newsrooms; Editing by Jon Boyle)