DAMASCUS   - Syria said on Wednesday it was questioning six Syrian officials who had been summoned to Beirut by U.N. investigators probing the killing of former Lebanese Prime Minister Rafik al-Hariri.

The interrogation of the officials effectively prevents them from going to Lebanon for questioning by the U.N. team until the Syrian panel dismisses them. Syria has denied any involvement in Hariri's death.

"They are expected to stay in Syria until the interrogation is concluded," Ibrahim al-Darraji, spokesman for the Syrian panel, which was set up in October to probe the killing, told Reuters.

He did not name the six but a Lebanese source has said they included Syrian President Bashar al-Assad's brother-in-law, Major General Asef Shawkat, head of Syria's powerful military intelligence.

Darraji said the fact that the six could not at present leave Syria "should not be seen as ... an acceptance or a rejection of the request of the international committee."

Earlier, the official news agency SANA said Syria had invited U.N. investigator Detlev Mehlis to Damascus to discuss cooperation with the Syrian probe.

Syria last month dismissed a U.N. report implicating its officials in the bombing that killed Hariri, saying it was politically motivated. A Security Council resolution demanded Syria cooperate fully with the probe or face unspecified action.

"DESIRED COOPERATION"

"We propose ... the signing of a memorandum of understanding with your committee to achieve the desired cooperation," Ghada Murad, head of the Syrian panel, said in the letter to Mehlis.

Murad, also Syria's general prosecutor, told Mehlis the panel was ready "for full cooperation and coordination with (the U.N.) to find the truth that we all seek".

SANA said the letter was sent to Mehlis on Tuesday. U.N. officials in New York they were aware of the Syrian invitation but had no comment.

Shawkat, who is married to Assad's sister Bushra, was among 10 Syrian officials interviewed in Damascus by the U.N. team in September. His name appeared in Mehlis's report to the Security Council last month.

Assad will address the nation in a televised speech on Thursday, in which he is expected to declare his desire to work with the U.N. probe and push ahead with political reforms.

Arab League Secretary-General Amr Moussa said on Wednesday after meeting Assad and Foreign Minister Farouq al-Shara he was optimistic about Syria's cooperation with U.N. investigators.

"Both in terms of coordination and cooperation, I am optimistic," he told reporters.

In Beirut, a Lebanese political source said Damascus appeared willing to cooperate with Mehlis but was seeking an understanding on details of the questioning.

"Though they are keen to show that they are cooperating, the Syrians want to clarify some points before responding to Mehlis's request," the source said.

He said Damascus was not comfortable with the questioning taking place in Lebanon, where four pro-Syrian Lebanese generals are already under arrest and charged in the assassination.

"(The Syrians) want to know whether the six will be questioned as suspects or witnesses, and under what law and whose jurisdiction would any of them be held and charged if Mehlis decided to do so." (Reuters)