More than 5,000 people are now believed to have been killed in the Syrian government's crackdown on protests, the United Nations human rights chief has told the UN Security Council.

Demonstrators protesting against Syria's President Bashar al-Assad gather during a march through the streets after Friday prayers near Adlb December 9, 2011. The largest signs read: "God is the Greatest" (L) and "Dignity strike" (R). Picture taken December 9, 2011. More than 14,000 people are estimated to have been detained and at least 300 children are among the dead, Pillay told the 15-member council. She estimated that at least 12,400 have fled into neighbouring countries since the anti-government protests erupted in March.(REUTERS/Handout) The UN's Navi Pillay said on Monday there were reports of increased attacks by opposition groups on President Bashar al-Assad's security forces but highlighted "alarming" events in the besieged protest city of Homs, according to diplomats in the closed meeting.

More than 14,000 people are estimated to have been detained and at least 300 children are among the dead, Pillay told the 15-member council. She estimated that at least 12,400 have fled into neighbouring countries since the anti-government protests erupted in March.

"It is my estimation that the total number of people killed since the protests began earlier this year is now likely to exceed 5,000. This situation is intolerable," Pillay said.

But Bashar Jaafari, Syria's UN ambassador, said the session was part of a "huge conspiracy concocted against Syria since the beginning" and said Pillay was neither objective nor fair.

"She is not genuine in all her approach, in the report she presented... She has trespassed her mandate, she allowed herself to be misused in misleading the public opinion by providing information based on allegations collected from 233 defectors," Jaafari said.

"How could defectors give positive testimonies on the Syrian government? Of course they will give negative testimonies against the Syrian government. They are defectors."

Responding to Jaafari's comment, Frej Fenniche, chief of Middle East section of the UN Human Rights Council, told Al Jazeera that the body was in contact with some people within both the Syrian government and its security forces. 

"Who said to Mr. Jaafari that we are not in contact with people within the army now and with people at a high level within the government?... We have contacts with officials on the basis of confidentiality."

"If the government is saying we are lying we can say: 'OK let [us] go into the country and we will see.'"

The Syrian authorities have not granted human rights observers access into the country.

The Security Council held a private briefing on Syria with Western nations stepping up pressure for the body to condemn the violence. Russia and China vetoed a resolution on the Syria crisis in October.

'Immoral stance'

But Russia's foreign minister on Tuesday said that Western accusations that it was blocking UN action condemning the Syrian regime's crackdown on the  opposition were "immoral" because the West was refusing to put pressure on armed opposition groups.

"There are those who refuse to put pressure on the armed, extremist part of the opposition and are at the same time accusing us of blocking the UN Security Council's work. I would call this position immoral," Sergei Lavrov said in televised comments.

Germany's foreign minister on Monday urged those countries blocking UN Security Council action on Syria to change their minds.

"I am really shocked about what I heard about the atrocities in Syria. We owe this to those who lost their lives," said Guido Westerwelle.

Gerard Araud, France's UN ambassador, said "history will judge the silence of some and the indifference of others" and that "the honour of the Security Council is at stake".

Pillay told the meeting that the Syrian protesters had remained largely peaceful.

"However, reports of armed attacks by opposition forces, including the so-called Free Syrian Army, against Syrian forces have increased," she said.

The death toll did not include Syrian security forces, she stressed. The Syrian government says more than 1,000 police and troops have been killed in the unrest.

Fresh clashes

Fresh clashes were reported on Tuesday between army deserters and regular troops in two Idlib villages as well as in Daraa province.

The UK-based Syrian Observatory for Human Rights reported that army defectors on Tuesday in Idlib's Bab al-Hawa road killed seven members of Syria's security forces in retaliation for an attack that cost the lives of 11 civilians.

Syrians voted on Monday in municipal elections and many closed their businesses and kept children home from school in several parts of the country in a show of civil disobedience against the government.

The head of the elections committee, Khalaf al-Ezzawi, said voting had taken place "in a democratic spirit," and turnout had been "good".

But activists mocked the election on their Facebook page.

"The election farce organised by the authorities was a failure in the city of Deir Ezzor where we think the turnout was no more than one per cent. The roads were empty the whole day," an activist said of the vote in the eastern city.

General strike

Meanwhile, the Syrian National Council opposition bloc said the "dignity" general strike launched Sunday was widely observed in 12 provinces against "all expectations".

Opposition activists say the ongoing strike, if widely heeded, could place added economic pressure on the government at a time when it is already struggling with growing international sanctions and isolation.

The opposition wants the strike to remain in force until the government pulls the army out of cities and releases thousands of detainees.

Al Jazeera's Nisreen El-Shamayleh, reporting from near the Jordan-Syria border, said that troops loyal to Assad were taking revenge against boycotting business owners.

"We heard reports that troops burned down at least 178 stores and shops in Deraa to try and take revenge against civillians who have shut down their stores and shops and are basically observing this general strike," she said.

Residents in the capital, Damascus, said business continued as usual on Sunday and Monday with shops, schools and other businesses operating normally.