Syria unrest: Activists say 20 killed in Homs Published duration 3 November 2011

media caption This video, released on Wednesday before the deal was announced, is said to have been shot in Homs

Tanks with machine-guns have opened fire in the Syrian city of Homs, killing at least 20 people, activists have reported.

The UK-based Syrian Observatory for Human Rights said the Baba Amr district came under heavy fire on Thursday.

Violence was also reported in other parts of the city.

It comes a day after the authorities in Damascus agreed to an Arab League plan calling on the government to pull the military out of cities.

The plan required Syria to withdraw all troops from urban areas and end all killing immediately.

The Arab League said Damascus had agreed to release all political prisoners and begin a dialogue with the opposition within two weeks.

The Syrian government also said it would allow journalists, rights groups and Arab League representatives to monitor the situation in the country.

At present foreign journalists are unable to move around Syria freely and information is tightly controlled and hard to verify.

'Lack of options'

Syrian opposition groups criticised the plan as an attempt by the regime to buy more time.

"The regime has accepted the Arab initiative out of fear of Arab isolation, its weakness and lack of options," a leading opposition figure, Burhan Ghalioun, wrote on his Facebook page.

"But its acceptance does not mean it will respect its clauses."

Mr Ghalioun is a senior figure in the Syrian National Council. Another member of the council, Samir al-Nashar, said it had met Arab League head Nabil al-Arabi to discuss the agreement with Damascus.

"We are not talking about a dialogue," he told AFP news agency.

"We offered to engage in negotiations to move from a authoritarian regime to a democratic regime. And we ask that Bashar al-Assad resign."

From Homs, video footage emerged purporting to show tanks firing in a built-up area on Thursday. The voice of the cameraman 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".