Damascus, Syria ? Facing possible economic sanctions, Syria argued Saturday that it cooperated fully with a U.N. probe into the assassination of a former Lebanese leader and accused anti-Syrian witnesses of lying to tie the Damascus regime to the murder.

But Saad Hariri, son and political heir of slain billionaire Rafik Hariri, praised the United Nations investigation and called for an international tribunal to try the alleged plotters.

Damascus sought for a second straight day to dispute a U.N. report that implicated Syrian and Lebanese officials in the Feb. 14 bombing that killed Rafik Hariri, a former prime minister and opponent of Syria’s domination of his country, and 20 others in central Beirut.

Hariri’s killing provoked Lebanese to hold mass demonstrations against Syria’s nearly three-decade military occupation and intensified international pressure on Damascus, leading to the regime withdrawing troops from its neighbor in April.

In the first arrest since the U.N. report was issued Thursday, police nabbed a Lebanese Islamic fundamentalist in Beirut early Saturday upon a recommendation by the U.N. team, security officials said on condition of anonymity as they were not authorized to give official statements.