By Yew Lun Tian

BEIJING The disappearance of China's Defence Minister Li Shangfu, who is being investigated for corruption, is just the latest recent case in which a senior official in President Xi Jinping's entourage has mysteriously vanished.

The disappearance is often the first discernible sign that an official has come under investigation by the feared Central Commission for Discipline Inspection - a watchdog under the Chinese Communist Party tasked with policing officials suspected of violating party regulations or state laws.

If the official is from the military, the investigating body is the People's Liberation Army's own Discipline Inspection Commission. Acts that come under scrutiny range from corruption to political disloyalty to extramartial affairs, the watchdog's announcements issued in the past show.

Past disappearances have lasted weeks or even months, such as another recent high profile case, that of former Foreign Minister Qin Gang, who is missing since June 25.

Here are some instances of recent disappearances:

LI SHANGFU, 65, DEFENCE MINISTER

China's public face of the military as the defence minister, Li is under investigation over the corrupt procurement of military equipment, 10 people familiar with the matter have told Reuters.

Li was last seen in Beijing on Aug. 29 giving a key-note speech at a security forum with African nations. Earlier that month, he visited Russia and Belarus. The probe started shortly after his return from that trip.

By Sept. 3, his ministry cancelled Li's trip to Vietnam for an annual defence meeting scheduled for Sept. 7-8, citing health reasons, according to Vietnamese officials.

QIN GANG, 57, EX-FOREIGN MINISTER

Qin was a political rising star until this July when he was stripped of the foreign minister title without explanation.

A former trusted aide to President Xi Jinping and former envoy to the United States, he had been allowed to retain his other title of State Councillor, a post that outranks the minister but has no real power by itself.

He was last seen on June 25 having meetings in Beijing with his counterparts from countries including Russia and Vietnam.

Qin had an extramarital affair while he was ambassador to the United States, the Wall Street Journal reported on Tuesday, citing people familiar with a briefing.

XIAO YAQING, EX-INDUSTRY MINISTER

Xiao, who helmed the ministry of industry and information technology, disappeared from public view in early July last year and about three weeks later, the state media said he was being investigated for corruption.

Xiao was especially prominent in his promotion of China's new energy vehicle industry, the world's largest. He was eventually expelled from the Communist Party for bribery and relieved of his government duties in December.

LI YUCHAO AND XU ZHONGBO, EX-ROCKET FORCE LEADERS

Another military general missing-in-action is Li Yuchao, 60, who was put in charge of China's conventional and nuclear missiles in January last year.

In July this year, Beijing announced a leadership shake-up at the Rocket Force and replaced Li with a navy general, detracting from the usual practice of picking someone from the same force to head it.

The Rocket Force also got a new political commissar, someone outside the force. Xu Zhongbo was replaced by an air force general from the Southern Theatre Command.

Neither Li Yuchao nor Xu Zhongbo have been seen in public for months.

(Reporting by Yew Lun Tian; Editing by Antoni Slodkowski and Michael Perry)