(Reuters) - A senior Chinese diplomat has been sacked and is under investigation for suspected corruption, the foreign ministry said on Friday, the first time a top diplomat has fallen victim to a sweeping campaign against graft.

Zhang Kunsheng is no long an assistant foreign minister as he was "suspected of violating discipline and is being investigated", the ministry said in a brief statement, using the usual euphemism for corruption. It provided no other details.

Media said Zhang was the most senior of the country's four assistant foreign ministers, who rank below the vice foreign ministers, and was in charge of the protocol department.

Qin Gang, who was the ministry's chief spokesman, had assumed the protocol position, Chinese newspapers said.

Assistant Foreign Minister Liu Jianchao will be acting chief spokesman, a role he previously had, the reports said.

President Xi Jinping has cracked down on corruption since assuming office two years ago, warning, as others have before him, that the problem is so bad it could affect the Communist Party's ability to maintain power.

While several senior heads have rolled, no senior diplomats had been caught up.

While the ministry is one of the only government departments which will regularly answer questions from foreign reporters and so has a high profile, it has little power or influence compared with other ministries.

The ministry was implicated in another scandal last year, when China's ambassador to Iceland vanished amid reports in overseas Chinese media that he had been arrested for passing on secrets to Japan. [ID:nL3N0SC17V]

The government has yet to account for what happened to him.