Beirut: A Lebanese spy chief once jailed in connection to the assassination of Lebanese Prime Minister Rafik Hariri gave testimony on Tuesday to the international tribunal tasked with trying the crime.

Jamil Sayyed, the former director of Lebanon's General Security, was called to the stand in the Netherlands as a witness for Hassan Oneissi, one of the four defendants on trial. All four are at large and are being tried in absentia.

Sayyed, who won a seat in Parliament in Lebanon's May 6 election, is expected to give testimony through Thursday.

He was detained months after the February 14, 2005, killing along with three other generals but released nearly four years later without charges.

The tribunal indicted five members of the militant Hezbollah group in the truck bombing that killed Hariri and 21 others. The five indicted and later put on trial in absentia included one of Hezbollah's top military commanders, Mustafa Badreddine, who was killed in Syria in 2016.

Hezbollah denies involvement in the murder and the group's leader, Sheik Hassan Nasrallah, has denounced the court as a conspiracy by his archenemies - the US and Israel.

Hariri also held Saudi citizenship.

Judge David Re apologised on behalf of the tribunal for Sayyed's alleged rough treatment while he was detained in Lebanon.