The 15-nation council is to meet on the Syria crisis amid growing concern over President Bashar al-Assad's military assault on pro-democracy protests, which is said to have killed about 2,000 people in five months.

UN Human Rights Commissioner Navi Pillay and humanitarian chief Valerie Amos are to give details of latest events in the strife-torn country at the briefing.

Pillay's report will say there is "evidence that Syria has committed grave violations of international human rights law," said one diplomat with knowledge of the report.

Pillay wants "a thorough, appropriate, international investigation" of the crackdown, the diplomat told AFP, speaking on condition of anonymity.

The UN rights official "is likely to suggest that the International Criminal Court would be appropriate," added another diplomatic source.

The UN human rights department "is expected to conclude that the allegations are so serious, and credible, that national level investigation conducted by the Syrians will be insufficient," added the source.

Only the Security Council can refer the Syria case to the ICC, which is based in The Hague.

Earlier this year the international body said the court should investigate events in Libya and the ICC issued arrest warrants in June for Libyan leader Moamer Qadhafi, his son and a close associate.

The Security Council has also referred Sudan's President Omar al-Bashir to the ICC over the Darfur conflict. Bashir is now wanted on genocide and crimes against humanity charges.

The European Union and United States has stepped up pressure on Assad's government with mounting sanctions moves. The Western powers face opposition in the Security Council to new sanctions from Russia, China and the emerging powers: Brazil, India and South Africa.

UN humanitarian chief Amos is negotiating with the Syrian government to let a humanitarian aid team assess the extent of the crisis in the country.

UN leader Ban Ki-moon spoke to Assad on Wednesday to reinforce the case, a UN spokesman said.

Assad first promised the UN secretary general in April that his government would negotiate a UN mission.

Amos told reporters she hoped the humanitarian team would get into Syria

"We hope that we are very nearly at the point where a mission will be able to go in and we will be able to make assessments," she told reporters.

The UN under secretary general said it would be a "priority" to get unconditional access to Syrian towns that have been the target of attacks by Assad's military. But she said negotiations were still going on.

The UN Security Council meeting starts at 1900 GMT on Thursday and will almost certainly be behind closed doors.

Copyright AFP (Agence France-Presse), 2011