Tanks mounted with machine-guns have opened fire in the Syrian city of Homs, activists have reported. It comes a day after authorities in Damascus agreed to an Arab League plan calling on the government to pull the military out of cities. The UK-based Syrian Observatory for Human Rights said the Baba Amr district of Homs came under heavy fire on Thursday. Unconfirmed reports say at least three people were killed in the city. On Wednesday, the Arab League said Syria had agreed to its proposals to end the violence. The plan requires Syria to withdraw all troops from cities and an immediate cessation to all killing. Under the plan Damascus also agreed to stop violence against protesters, release all political prisoners and begin a dialogue with the opposition within two weeks. The Syrian government also agreed to allow journalists, rights groups and Arab League representatives to monitor the situation in the country. Syrian opposition groups criticised the plan as an attempt by the regime to buy more time. New video Video footage emerged on Thursday from Homs purporting to show tanks firing in a built-up area on Thursday. The voice of the camera man gives the date and mentions the previous day's agreement with the Arab League. Protests against the rule of President Bashar al-Assad started in March but have become increasingly violent. The government has tried to put down the demonstrations using the security forces and pro-government militia. Opponents of the regime have taken up arms and been joined by soldiers who have defected. At least 3,000 people have been killed in the unrest in Syria, while hundreds of others have disappeared. The government of Mr Assad - who took over from his father as president in 2000 - says the violence is being carried out by "armed gangs" and "terrorists". More than 1,000 security personnel have lost their lives in the fighting, the government says. Foreign journalists are unable to move around Syria freely and information is tightly controlled, making reports difficult to verify.