UNITED NATIONS, (Reuters) – The U.N. Security Council voted unanimously on Thursday to extend for six months the international probe into the murder of a Lebanese leader and told Syria it was not cooperating fully with investigators.

After a day of wrangling, mainly between Russia and Western powers on how to characterize Syria”s actions, the 15-nation council expressed &#34extreme concern&#34 that Syria had yet to provide U.N. investigators &#34full and unconditional cooperation.&#34

The mandate for the probe into the death of a former prime minister, Rafik al-Hariri, by a truck bomb in Beirut on Feb. 14 would have expired at midnight (0500 GMT). The resolution extending it to June 15 was initiated by France and co-sponsored by the United States and Britain.

The resolution also authorizes the U.N. 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 U.N. inquiry, on Monday released a 25-page report saying new evidence had reinforced his earlier judgment that Syrian intelligence officials and their Lebanese allies, were involved in the killing.

He said Syria had stalled the probe but cooperation had improved this month.

The Security Council resolution demanded that Syria respond &#34unambiguously and immediately&#34 in areas the commission found necessary, without mentioning them.

Syria has vehemently denied its involvement or that it has been slow to respond to requests from Mehlis, who will be returning to his post in Berlin as soon as a replacement is named.

&#34We are fully confident that Syria is innocent,&#34 its U.N. ambassador, Fayssal Mekdad, told reporters. &#34Syria would never be behind these crimes. This is not our policy.&#34

Commenting on the text, Mekdad said Syria had &#34many friends&#34 who rejected &#34threats and blackmail.&#34

Russian Ambassador Andrei Denisov told the council Moscow had proposed its own &#34more balanced&#34 amendment but France and the United States refused to remove unnecessary &#34negativism&#34 towards Syria.

&#34We continue to oppose unwarranted pressure on Damascus,&#34 Denisov said.

The assassination of Hariri, an opponent of Syrian domination of his country, transformed Lebanon”s political landscape, prompting a pullout of Syrian troops after three decades.

A string of politically-motivated attacks followed. On Monday, a leading anti-Syrian journalist and lawmaker, Gebran Tueni, and three others were killed by a car bomb in a suburb near Beirut.

&#34We are making it clear to the government of Syria they can”t run, they can”t hide,&#34 U.S. Ambassador John Bolton told reporters before the vote. &#34The 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 U.N. investigation to cover other terrorist killings since Oct 1, 2004, and for the United Nations to form a tribunal of an &#34international character&#34 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 authorizes the U.N. commission to provide &#34technical assistance&#34 to Lebanon.

On the tribunal, the resolution asks U.N. Secretary-General Kofi Annan to help Lebanon identify the scope of such a court but did not agree to establish it.

The most controversial issue facing the council is a resolution, adopted Oct. 31, that threatened &#34further action&#34 against Syria if it did not cooperate fully with Mehlis”s team.

This could lead to sanctions, either against individuals or the country as a whole, but divisions in the council may prevent any punitive action.