China replaced two leaders of an elite unit managing its nuclear arsenal, triggering speculation of a purge.

General Li Yuchao who headed the People's Liberation Army's (PLA) Rocket Force unit and his deputy had "disappeared" for months.

Former deputy navy chief Wang Houbin and party central committee member Xu Xisheng were named as replacements.

This is the biggest unplanned shake-up in Beijing's military leadership in almost a decade.

"The latest purge is significant… [as] China is undertaking one of the most profound changes in nuclear strategy in decades," said Lyle Morris, a foreign policy and national security fellow at the Asia Society Policy Institute.

"[President] Xi [Jinping] has consolidated control of the PLA in unprecedented ways, but that doesn't mean it's complete. Xi is still worried about corruption in the ranks and has signalled that absolute loyalty to the [party] has not yet been achieved," he said.

Mr Xi is also chairman of China's top military command, the Central Military Commission.

At a meeting late last month, Mr Xi stressed the need to focus efforts on "addressing prominent issues faced by party organisations at all levels, in aspects such as maintaining the party's absolute leadership over the military", Chinese state media reported.

Beijing has not commented on the whereabouts of Gen Li and his deputy General Liu Guangbin, but a South China Morning Post report last week suggested that the commission's anti-corruption arm had launched an investigation into the two men, as well as Gen Li's former deputy Zhang Zhenzhong.

The report cited two unnamed sources.

Mr Wang's and Mr Xu's new appointments came a day before the 96th anniversary of the PLA's founding on 1 August. They were announced at a ceremony at the commission's headquarters in Beijing.

Both have been promoted from the rank of lieutenant general to full general which in China marks the highest rank for active service officers.

Mr Morris said Gen Li's downfall, together with the recent replacement of former foreign minister Qin Gang, presents one of the biggest leadership challenges for Mr Xi in recent times.

Mr Qin had been absent from public commitments for a month before he was replaced by his predecessor Wang Yi last week. No explaination was given for his removal.

In 2014, a broad purge among China's military ranks saw former deputy chairs of the Central Military Commission Xu Caihou and Guo Boxiong ousted and prosecuted for corruption. Guo was sentenced to life in jail by a military court, while Xu died before his trial.