Lebanon has taken its first steps in response to the UN report into the murder of former Prime Minister Rafik Hariri, arresting one man.
Mahmoud Abdul Al allegedly made calls just before the car bombing
The report says the man, Mahmoud Abdul Al, reportedly a member of a pro-Syrian Islamic group, phoned Lebanon's president minutes before the attack.
However, officials later denied earlier reports that a travel ban had also been put on 11 senior figures.
Syria denies involvement in the killing of Mr Hariri in February.
On Sunday, Deputy Foreign Minister Walid Moallem denied he had threatened Mr Hariri less than two weeks before the bombing that killed him.
"This is totally untrue," he said on Syrian state television.
The UN says it based its accusation on a tape of the conversation, and said Mr Moallem had not told the truth in his testimony about his 1 February meeting with Mr Hariri.
The latest moves came as UK Foreign Secretary Jack Straw said Syria had to realise it could not carry out political killings.
His US counterpart Condoleezza Rice said there was evidence that, at the very least, Syria had failed to co-operate with the investigation.
KEY UN FINDINGS
Assassins had considerable resources and capabilities
Evidence suggests both Syria and Lebanon were involved
Crime was prepared over several months
Hariri's movements and itineraries were monitored
Highly unlikely Syrian or Lebanese intelligence were not aware of assassination plot
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Speaking in a joint press conference with Mr Straw, she said the issue would have to be discussed in the UN Security Council.
The UN report accuses Mr Abdul Al of phoning Lebanon's pro-Syrian President Emile Lahoud minutes before the killing.
Mr Lahoud denies receiving the call. His statement also says that a call made to a phone in the president's office did not mean the caller had spoken to the president.
But the UN report has prompted renewed calls for the president to resign, which he has rejected.
Mr Abdul Al is later alleged to have contacted one of four pro-Syrian Lebanese generals who have already been arrested in connection with the murder.
Mr Abdul Al's brother, Ahmed, is also mentioned in the UN report as a key figure in any ongoing investigation.
The report says that around the time of the assassination of Mr Hariri, he had extensive phone contact with Syrian security officials in Lebanon, as well as Lebanese officials who have since been charged with the murder.
In a separate development, Lebanese security officials were reported to have been instructed to prevent 11 high-level figures from leaving the country.
But the country's Justice Minister, Charles Rizq, denied the reports in a subsequent BBC interview.
Several members of the UN Security Council have backed a US call for an urgent meeting over the findings of the UN report.
Released late on Thursday, it implicated Syrian officials and their Lebanese allies in the February assassination.
Meanwhile the leader of Lebanon's Druze community, Walid Jumblatt, backed a call by Mr Hariri's son, Saad, for an international tribunal after investigations were complete.
Syria on Saturday repeated its long-standing denial of involvement in the killing of Mr Hariri and 19 others.
It offered a promise to co-operate further with the investigation, but the BBC's Ian Pannell in Damascus said it was unclear what that meant or whether it would satisfy Syria's many critics.
Mr Straw has said the Security Council will consider imposing sanctions on Syria.
A coalition of anti-Syrian politicians led by Saad Hariri won a majority in Lebanon's elections earlier this year.
The victory followed the pull-out of thousands of Syrian troops stationed in Lebanon as part of a peace deal ending years of civil war.
The Syrian withdrawal was the result of intense international pressure and massive anti-Syrian street protests in Lebanon, prompted by Mr Hariri's assassination on 14 February.