Ahead of the observers' arrival in Homs, the army pulled back heavy armour from the Baba Amro neighbourhood of the city, after activists said 34 people were killed overnight. Eleven tanks pulled out about 7am local time, said Rami Abdel Rahman, the head of the observatory. The observer mission is part of an Arab plan endorsed by Syria on November 2 that calls for the withdrawal of security forces from residential areas, a halt to violence against civilians and the release of detainees.
Since signing the deal, Mr Assad's regime has been accused of intensifying a bloody crackdown on anti-government protests, which have shown no signs of abating since they erupted in March.
The UN says more than 5000 people have lost their lives.
The bloodshed in Homs has sparked a mounting international outcry and opposition calls for foreign intervention. Burhan Ghaliun, the leader of opposition umbrella group the Syrian National Council, urged UN and Arab League intervention "to put an end to this tragedy" and called on the UN Security Council to "adopt the Arab League's plan and ensure that it is applied".
On Sunday, the Syrian National Council said Homs was besieged and facing an "invasion" from some 4000 troops deployed near what has become a focal point of the uprising against Mr Assad. Syrian foreign ministry spokesman Jihad Makdisi said the observer "mission has freedom of movement in line with the protocol" Syria signed with the Arab League. Under that deal, the observers are banned from sensitive military sites. Meanwhile, opposition leaders charge that Syria agreed to the mission after weeks of prevarication in a "ploy" to head off a threat by the 22-member League to go to the UN Security Council over the crackdown.
Analysts warn that the Arab League-formed monitoring mission comprises Syrian sovereignty.
