Beirut, Lebanon ? The chief U.N. investigator into the assassination of former Lebanese Prime Minister Rafik Hariri said in remarks published Saturday that he believed Syrian authorities were behind the killing.

It was the first time that Detlev Mehlis has unequivocally accused Syria of responsibility for Hariri’s assassination since opening the U.N. probe in June.

When asked by the London-based Saudi newspaper Asharq al-Awsat if he was firmly convinced that Syria was behind Hariri’s killing, Mehlis replied, “Yes.”

When asked whether he was directly accusing the government of Syrian President Bashar Assad, Mehlis said, “Let’s say the Syrian authorities.” He declined to elaborate.

Syria has denied involvement.

Mehlis also said he saw a link between this week’s assassination of anti-Syrian journalist and lawmaker Gibran Tueni and a string of bombings that has rocked Lebanon since Hariri’s assassination in February.

In a new report this week, Mehlis said fresh evidence had strengthened his belief that the Syrian and Lebanese intelligence services had a hand in the Feb. 14 car bombing that killed Hariri and 20 others in Beirut. The report said there were 19 suspects so far, including six high-ranking Syrian officials.

Hariri’s assassination set off anti-Syrian street protests in Lebanon and intense international pressure that forced Damascus to withdraw its troops from Lebanon a few months later, ending nearly three decades of military domination.