Syrian opposition activists said on Wednesday that security forces still had armoured vehicles stationed in city streets ready to act against protesters even though Arab League peace monitors said they had withdrawn.

Opposition groups in the cities of Idlib in the north, central Homs and Deraa in the south said the army had hidden armour in dugouts and replaced tanks with blue armoured vehicles said to belong to police forces.

An Arab League mission arrived in Syria last week to verify whether the government was implementing a peace plan under which it had agreed to withdraw its military presence from restive areas and to release thousands of prisoners detained since the uprising against President Bashar al-Assad began last March.

League Secretary General Nabil Elaraby said in Cairo on Monday the monitors had reported back that state forces had withdrawn from residential areas. The mission was ensuring a halt to bloodshed and had secured the release of about 3,500 prisoners, he said.

We are not seeing the release of detainees or the true removal of a military presence from the streets, said Rami Abdelrahman, head of the British-based Syrian Observatory for Human Rights.

Army tanks have been replaced with police armoured personnel carriers that still have the capability to shoot heavy weaponry.

Videos uploaded by activists on the Internet showed armoured vehicles hidden behind high dirt barriers.

Nabil Elaraby, you are in Cairo and we're in Baba Amr. Here are the tanks and there are your monitors, said one activist in a video uploaded on the Internet which showed a team of orange-vested men who appeared to be League monitors standing near an armoured vehicle behind a barrier.

Such footage is impossible for Reuters to verify and Syria has barred entry to most foreign journalists.

BLATANT INTERFERENCE

The Syrian government on Wednesday rejected accusations from Washington that it was failing to live up to its agreement with the Arab League.

Washington accused the government was trying to stoke more violence to justify retaliation.

Such a statement is offensive to the Arab League...because it is a blatant interference in the core of its work, the sovereignty of its states and an unjustified attempt to internationalize (the Syria crisis), Foreign Ministry spokesman Jihad Makdesi said in a statement.

This is a pre-emptive stance that damages the performance of the Arab monitors' mission prior to their first initial report.

The mission is expected to report on its first week of work by end of this week.

Activists said the monitors visited the main prison in Homs, a hotbed of protest. They were greeted with chants of freedom, freedom and the people want the fall of the regime, the activists said, citing leaked messages from detainees and prison guards.

The security forces moved some of the detainees but the numbers are so huge they couldn't move them all, said Homs activist Abu Rami. They moved some detainees to military bases and moved away the ones who are in bad health.

Under the agreement to allow in the monitors, the mission cannot enter military sites. Last week, the U.S.-based Human Rights Watch said security forces were moving prisoners into military facilities to avoid the monitors.

Rights groups say there may be over 30,000 in prisons and activist tallies put the death toll since the team's arrival last week between at least 130 and 390 people.

More than 5,000 people have been killed in the crackdown on protests, according to the United Nations. Damascus says it is fighting Islamist militants steered from abroad that have killed at least 2,000 of Assad's forces.

(Additional reporting by Khaled Yacoub Oweis in Amman; Editing by Angus MacSwan)