An advance team for a delegation of Arab League monitors has arrived in the Syrian capital, Damascus.
The observers, due to arrive by the end of the month, are part of an initiative aimed at ending the violent crackdown on anti-government protests.
Damascus blames the unrest on "armed gangs" seeking to destabilise Syria.
The UN says some 5,000 people have been killed in Syria since protests began in March but rights groups say the figure is much higher.
In a rebuttal to the UN, Syria state news agency Sana said on Thursday that more than 2,000 members of the security forces had been killed since anti-government protests erupted in March.
"In response to a fallacious (UN) report on the situation in Syria, we have informed the office of the UN High commissioner for Human Rights that the number of martyrs has surpassed 2,000 members of the security forces and the army," the report said.
The Arab League advance party, accompanied by members of the media, arrived in Syria late on Thursday to prepare for the arrival of the full delegation, which will have a one-month mandate that can be extended by another month if both sides agree.
"We arrived in Damascus safely," Waguih Hanafy, senior aide to Arab League chief Nabil Elaraby, said from Damascus. He said the monitors could be sent before the end of December. The mission is expected to be 150-strong when complete.
The observers will oversee Syria's compliance with the league's initiative, which calls for attacks to stop, troops to withdraw from the streets and detained protesters to be freed.
Freedom of movement
Damascus's decision to admit them was announced on Monday, after weeks of delays.
Syrian Foreign Minister Walid Muallem said they would be allowed freedom of movement and be protected by the government.
But critics of President Bashar al-Assad are sceptical about his decision, saying it is a ploy and he is simply playing along with the diplomatic process in an attempt to stave off more stringent UN action.
Radwan Ziadeh, a spokesman for Syria's main opposition coalition, the Syrian National Council (SNC), told the BBC: "The Assad regime did not implement or accept the Arab League's initiative. It's true that they signed it but there is no action. It's only a signature on some papers.
"We gave them some of the hotspots in the different cities in Syria and we gave them instructions and we are in close co-ordination with the Arab League."
"But our position is that the Arab League is a very weak institution and they cannot actually protect the civilians. This is why we call [on] the Arab League to refer the case to the [United Nations] Security Council."
Activists point to an upsurge in attacks on anti-government protesters this week as evidence that Mr Assad is attempting to stifle unrest quickly.
Activists groups said at least 30 people had been killed by government forces on Thursday, mainly in the central city of Homs and in north-western Idlib province.
The SNC, which is based outside Syria, says at least 250 people have been killed this week in Idlib.
Journalists are not allowed to report freely in Syria so details are hard to verify.
The BBC's Jim Muir, who is monitoring events from neighbouring Lebanon, says Syrian authorities may well be "clearing up unfinished business" ahead of the arrival of the monitors, with reports suggesting the security services are acting against army deserters and civilians trapped in a valley.
Meanwhile, Russia is coming under pressure to speed up work on its draft UN resolution condemning the violence.
Moscow surprised diplomats by submitting the draft last week but there has been little progress since.
Russia - along with China - vetoed a European resolution in October which threatened sanctions against Damascus if the killing continued. But last week it submitted its own draft, which condemned both sides without mentioning sanctions.
On Thursday, the US issued fresh travel advice for Americans, urging "US citizens currently in Syria to depart immediately".