An estimated 400 people, an average of 40 a day, have been killed in Syria in the days following the arrival of the Arab League monitors in the country, a top UN official has said.

UN Under Secretary General for Political Affairs B. Lynn Pascoe on Tuesday briefed the 15-nation Security Council on the situation in Syria in a closed door meeting.

Pascoe's briefing came the same day a defiant Syrian President Bashar Al-Assad said he will not step down and blamed a foreign conspiracy for the country's nearly year-long bloody uprising.

Later talking to reporters here, US Ambassador to the UN Susan Rice said the briefing the Council received was 'alarming by any standard'.

"The Under-Secretary-General noted that in the days since the Arab League monitoring mission has been on the ground, in fact, some estimated 400 additional people have been killed, an average of 40 a day, a rate much higher than was the case before their deployment," Rice said.

Further, at least two of the monitors of the Arab League have also been 'roughed up, harmed, harassed' while they were carrying out their work. According to the United Nations, more than 5,000 people have been killed since the anti-government protests began last March.

Syrian government, however, says 2000 security personnel were killed by armed terrorists. She said the unabated violence is a clear indication that the Syrian government is not using the opportunity of its commitment to the Arab League to end violence but is instead 'carrying out further acts of brutality against its population even often in the presence of those monitors'.

Rice said Assad should step aside and pave the way for a democratic government in keeping with the wishes of the Syrian people.

"Unfortunately, rather than take that approach, we heard the vitriol of President Assad's speech today and further belittling by him of the Arab League, which we found offensive."

In response to Assad's claims that the uprising in his country was the handiwork of a foreign conspiracy, Rice said for him to make such claims "is frankly an insult to the people of Syria who are dying on the streets at the hands of their own government as they try to bring about, through peaceful means, a more responsive government."

Rice said it is high time the UN Security Council passes a strong resolution that supports the Arab League and considers putting sanctions on the Syrian regime.

Countries like Russia and China are, however, not in favour of imposing sanctions on Assad's regime, as they believe government rebels are equally to be blamed for the bloodshed.

"Unfortunately, after a bit of a show last month of tabling a resolution, the Russians inexplicably have been more or less AWOL in terms of leading negotiations on the text of that resolution," Rice said, referring to a draft resolution Russia tabled before the Council on Syria.

Russia's UN Ambassador Vitaly Churkin said his country was working on a draft resolution on Syria 'all the time' adding that 'members of the council continue to remain rather far apart'.

"One of the reasons we have not been throwing various texts around is that we have been following the progress of the Arab League monitoring mission and on January 19 this is going to be another sort of milestone," Churkin said.

The Arab League mission is due to provide its report on the ground situation in Syria on January 19. Speaking after Rice, Syria's UN envoy Bashar al-Jaafari said the killings in his country were the result of incitement by western powers.

"There is no Syrian interest whatsoever to harm the credibility and the safety and the security of the Arab envoys," he said.

"These victims are falling in Syria because of those who are still insisting on instigating and inciting violence. And I am sure you have heard a lot of these incitement calls from the same countries, from the same representatives who have just spoken to you," Ja'afari said.