General Kenaan, 63, was one of several top officials caught up in a UN investigation into the murder of Lebanon's former prime minister, Rafik Hariri, on 14 February this year.

He was Syria's intelligence chief and top official for two decades in Lebanon, which was dominated by Syria until its military withdrawal earlier this year.

His death yesterday comes less than a fortnight before the final UN report into the murder, due to be issued by 25 October. General Kenaan's chief aide said that he had shot himself in his office in the interior ministry. "General Kenaan left his office to go home, then he came back after three quarters of an hour, took a gun from the drawer and fired a bullet into his mouth," General Walid Abaza said.

In Lebanon, Prime Minister Fuad Saniora said he had no details about the death. But a prominent Lebanese legislator and journalist, Gebran Tueni, cast doubt on the suicide report. "It is not known for sure if he committed suicide, or was made to commit suicide," Mr Tueni told Al-Arabiya television from Paris. "In Syria, there are some people who want to hide the facts, and don't want everything about the Syrian period in Lebanon to be known."

Hours before his death, General Kenaan contacted a morning broadcast of Voice of Lebanon radio station to give what he called his "last statement". He was broadcast saying: "We exerted joint efforts and spared no blood and this resulted in the liberation of Lebanon at a time that it was impossible to do so without Syria."

In the interview, General Kenaan denied a report that he had told the UN investigators about corrupt officials during Syria's control of its western neighbour.

Analysts say the Syrian government is quietly preparing for the UN report, expected to implicate Syria's intelligence regime in the bombing, by consolidating its power, readying a diplomatic counteroffensive, and taking steps to guard against any sanctions.

Damascus has denied any involvement in the Hariri bombing, but it immediately came under heavy international pressure to relinquish its political and military control on Lebanon.

Syrian President Bashar al-Assad told CNN that he was not aware of any evidence to suggest his country had a hand in the 14 February bombing that killed Hariri and 20 others in Beirut. "If indeed there is a Syrian national implicated in it, he would be considered a traitor and most severely punished," Mr Assad said.

But his government is reportedly planning a diplomatic offensive to discredit an incriminating report. Syria would appeal to China, India and Russia to help block a UN resolution and possible sanctions.

The interior minister in Syria controls the police. But before General Kenaan was promoted to minister in 2004, he was Syria's intelligence chief in Lebanon. Syrian intelligence named and fired Lebanese officials and controlled every aspect of political and military life.

Lebanese newspapers have reported General Kenaan was among seven senior Syrian officials questioned last month by the UN team investigating Hariri's murder. The other officials included Syria's last intelligence chief in Lebanon, Brigadier-General Rustum Ghazale and his two aides.

The investigators have named as suspects four Lebanese generals who are close to Syria, and Lebanon has arrested them. Syrians expressed their fears General Kenaan's suicide would provoke more international pressure over the country's role in Lebanon.

General Kenaan is survived by a wife, four sons and two daughters.