Radio Damascus on Monday reaffirmed that Syria was prepared to cooperate fully with the UN inquiry led by German prosecutor Detlev Mehlis but also seethed over continued accusations that it was implicated in the assassination of al-Hariri.
"Syria has nothing to hide and has no fear about the Hariri affair. On the contrary, it has invited Mr Mehlis to Damascus so that he can meet the people he would like to," the radio said in its daily commentary.
"Nobody has any doubts about the honesty of Mehlis or about his capacity to discover the truth. But the leaders in Washington and other Western countries are trying to use this criminal affair to damage Syria after the failure of all their attempts to tarnish its image" the radio said.
"The plan hatched against the region will damage Syria and also the whole Arab world. Besieging Syria and breaking its historic links with Lebanon are aimed at imposing foreign domination" over the two countries, it argued.
Syria has rejected allegations of involvement in the 14 February bomb blast in Beirut that killed al-Hariri.
Mehlis wants to interrogate the former head of Syrian military intelligence in Lebanon, Rustom Ghazali, and two other former top agents in Beirut. He is to hold talks in Syria on Saturday.
A report in Berlin on Monday said UN investigators have uncovered leads in Beirut that point to high-level involvement in the plot to kill al-Hariri.
The Der Spiegel weekly news magazine said the arrest of four top aids of pro-Syrian President Emile Lahoud at the weekend "can mean a breakthrough and bring Syria to book".
A massive bomb killed al-Hariri
on 14 February
"The UN team... believes it can now prove that those arrested plotted the murder in an attempt to silence the former anti-Syrian prime minister," it said.
The leads include fingerprints found in an empty apartment in Beirut where it is believed the plot to kill al-Hariri was hatched and a car that was seen following his convoy on 14 February.
The car belongs to Lebanon's former army intelligence director Raymond Azar, according to Der Spiegel, which is regularly reporting on the UN investigation led by Mehlis.
It said Mehlis has found a trail of telephone calls that "leads directly to the highest levels of the security apparatus".
A Lebanese judge on Saturday ordered the four suspects to be held in custody after he questioned them about the murder, and their arrest is seen as the first major step towards a trial in the case.
They are Azar, presidential guard commander Mustafa Hamdan, former general security chief Jamil al-Sayed and ex-internal security head Ali al-Hage.
Metlev, however, has said that he believes they are "only part of the picture" that makes up the plot to kill al-Hariri.