The Lebanese authorities discovered two common graves at the weekend near what used to be the headquarters of Syria's intelligence operation in Lebanon.

Troops aided by bulldozers recovered at least 25 bodies from graves on an onion farm near the town of Anjar, in the east of the country.

Most of the bodies, reports suggest, date from the late 1980s, the final phase of Lebanon's 15-year civil war, or the early 1990s, when Syria controlled the entire country.

Lebanese media yesterday reported that a more recent buried body had been found at one of the sites and that the United Nations investigation of the murder of Rafiq Hariri, the country's former prime minister, has asked to check its identity.

There are reports that the investigators want to ascertain whether the remains are those of Ahmad Abu Adass, a young Palestinian who had claimed the suicide bombing in a pre-recorded video, but who may have been used as a decoy.

The UN investigation, headed by the German prosecutor Detlev Mehlis, in an interim report six weeks ago, implicated Lebanese and Syrian intelligence officials in the blast that killed Mr Hariri and 20 others.

After the assassination, mass demonstrations in Lebanon combined with international pressure led to a withdrawal of Syrian troops from the country after a near 30-year presence. Syria has denied responsibility for Mr Hariri's murder.

Damascus yesterday denied knowledge of the common graves found this weekend. It said the bodies date from Lebanon's civil war. Some 17,000 Lebanese are said to be missing from that time and the subsequent Syrian presence.

The UN team investigating the murder of Mr Hariri is expected to question five senior Syrian intelligence officers today in Vienna.