After a day of wrangling, mainly between Russia and Western powers on how to characterise Syria's actions, the 15-nation council expressed "extreme concern" on Thursday that Syria had yet to give UN investigators their "full and unconditional co-operation".
The resolution on a mandate for the probe into the death of Rafiq al-Hariri, a former prime minister of Lebanon, was extended to 15 June.
It was initiated by France and co-sponsored by the United States and Britain.
The resolution also authorises the UN commission to provide technical assistance to the Beirut government investigating a string of other politically motivated murders or attempted killings in the last year.
Detlev Mehlis, the German prosecutor who headed the UN inquiry, released a 25-page report on Monday, saying new evidence had reinforced his earlier judgment that Syrian intelligence officials and their Lebanese allies were involved in the killing.
"The end game of this exercise is to get to the bottom of the Hariri assassination and to bring to justice anybody - anybody - responsible for it"
US ambassador to the UN
He said Syria had stalled the probe but co-operation had improved this month.
The Security Council resolution demanded that Syria respond "unambiguously and immediately" in areas the commission found necessary, without mentioning them.
Commenting on the text, Fayssal Mekdad, Syrian ambassador to the UN, said Damascus had "many friends" who rejected "threats and blackmail".
Andrei Denisov, the Russian ambassador, told the council that Moscow had proposed its own "more balanced" amendment but France and the United States refused to remove unnecessary "negativism" towards Syria.
"We continue to oppose unwarranted pressure on Damascus,"
The US ambassador, however, urged Syria to co-operate.
Mekdad said Damascus had
"We are making it clear to the government of Syria they can't run, they can't hide," John Bolton, the US ambassador, told reporters before the vote.
"The end game of this exercise is to get to the bottom of the Hariri assassination and to bring to justice anybody - anybody - responsible for it."
Lebanon had asked the UN investigation to cover other terrorist killings since 1 October 2004, and for the United Nations to form a tribunal of an "international character" to try suspects.
But Russia, China and Algeria resisted the original text, which would have expanded the investigation at the discretion of the inquiry team.
Instead the resolution authorises the UN commission to provide "technical assistance" to Lebanon.
On the tribunal, the resolution asks Kofi Annan, the UN secretary-general, to help Lebanon identify the scope of such a court but did not agree to establish it.