China's President Xi Jinping on Tuesday sacked Defense Minister Li Shangfu, who has not been seen in public since early September, according to a government notification.
He also replaced two ministers. A new defense chief has not yet been named.
Xi signed a presidential decree to remove Li as state councilor and defense minister.
Li, 65, was also removed from a Xi-led Central Military Commission, where he served as one of its six members.
Xi's decisions were approved by the 175-member Standing Committee of the National People's Congress.
Li was last seen in late August when he addressed a China-Africa security forum in Beijing.
The possibility of corruption behind Li's sacking has not been ruled out.
Xi also removed former Foreign Minister Qin Gang, 57, as state councilor, who was off the public radar for more than a month before being sacked in July.
Reports claimed an extra-marital affair behind Qin's removal.
The post of state councilor is a rank above Cabinet minister, in China.
The prolonged disappearance and sacking of top officials under Xi's unprecedented third term as president has also been called a "leadership shock."
Beijing has not given any official reason for the sacking of a couple of its top faces.
In March, the Communist Party's National Party Congress endorsed Xi's new Cabinet with 26 departments.
Xi also removed Wang Zhigang from Minister of Science and Technology and appointed Yin Hejun, 60, in his place.
China's Minister of Finance Liu Kun was replaced by Lan Fo'an, 61.
Before being picked up as defense chief, Li was sanctioned by the US for leading Beijing's defense cooperation with Russia.
Washington refused to lift sanctions, while Beijing resisted any high-level communication with the Pentagon until the U.S. waived off the restrictions.
