|Demonstrators surrounded cars carrying Arab League observer who were visiting areas near Homs [Reuters]
Activists have accused the Syrian government of misleading Arab League observers by taking them to areas loyal to the government, changing street signs to confuse them, and sending supporters into hostile neighbourhoods to give false testimony.
The month-long observers mission, which started on December 27, offers a rare outside glimpse into a country where a government crackdown on a 9-month-old uprising has killed more than 5,500 people, according to the UN.
But there are fears that government loyalists have corrupted the observers process beyond repair.
There was no immediate comment from the Arab League on Wednesday, but Jihad Makdissi, the Syrian foreign ministry spokesman, denied the allegations.
"We don't interfere in the mission's job," he told the Associated Press news agency.
He said that government escorts were necessary to protect the observers.
Among other things, opposition activists said government loyalists were painting military vehicles blue to make them look like police vehicles.
They called this a ploy that allows the government to claim it has pulled the army out of heavily populated areas in accordance with the Arab League plan that was supposed to end the government's crackdown on dissent.
The plan requires the government to remove security forces and heavy weapons from city streets, start talks with opposition leaders and free political prisoners.
Syria agreed to it on December 19, paving the way for the observers to enter. About 100 monitors are in the country now to assess whether the regime is complying.
But the Arab League has acknowledged that killings have gone on, even with the observers on the ground.
Activists put the death toll at more than 400 people since December 21.
As the observers continued their work on Wednesday, security forces and pro-government groups shot dead at least 12 people, nine of them in central Homs province, activist groups said.
The secretary-general of the Arab League, Nabil Elaraby, said in Cairo that the regional body would not cut short the observers mission in Syria.
An Arab diplomat on Tuesday said that the 22-member organisation would consider pulling out of Syria because the killings were continuing despite the observers' presence.
The Arab League has claimed some victories for the monitors, including the withdrawal of heavy weapons from cities and release of thousands of prisoners.
But Syria has banned most foreign journalists and prevented independent reporting, making it difficult to verify any claims from either side. Interviews with activists and witnesses over the past week indicate there have been clear signs of interference with the mission.
"The observers are going to areas known to be loyal to the regime," Rami Abdul-Rahman, head of the British-based Syrian Observatory for Human Rights, said.
The Arab League monitors made "mistakes" in Syria during their mission to investigate the crackdown, Kuwait's state news agency quoted Sheikh Hamad bin Jassim Al Thani, the prime minister of Qatar, as saying.
"This is the first experience for us ... and I said we must evaluate the types of mistakes it [the mission] made and without a shadow of a doubt I see mistakes, even though we went in [to Syria] to observe, not to stop the violence," he said after a meeting with Ban Ki-moon, the UN secretary-general, in New York, according to the KUNA report on Thursday.
In-depth coverage of escalating violence across Syria
Sheikh Hamad, who also chairs an Arab League taskforce on Syria, did not elaborate on the "mistakes", but said he was seeking "technical help" from the UN.
For its part, Syria announced on Thursday the release of 552 people who were detained over their involvement in political unrest and who had "no blood on their hands".
The official SANA news agency said that 2,645 prisoners were also released in November. Rights groups and the UN estimate that several thousand people have been arrested since anti-regime protests erupted in mid-March.