The struggle between supporters and opponents of Syrian President Bashar al-Assad has spilled into Lebanon after several violent clashes were reported.

Syrians opposed to al-Assad clashed with supporters of the president in Beirut, the Lebanese Daily Star reported.

The confrontation took place in the Baajour neighbourhood, near the Lebanese University campus.

Although supporters and opponents of the regime quickly fled the scene, police said an investigation has been launched.

Similar clashes were also reported in the capital's southern suburbs.

Confrontations were also reported between members of al-Jamaa al-Islamiya, a Lebanese branch of the Muslim Brotherhood, and members of the Arab Socialist Ba'ath Party in Lebanon in the coastal city of Sidon.

A source close to al-Jamaa al-Islamiya told the Daily Star clashes began after members of the Ba'ath Party took down posters calling on people to support the revolution.

Jamaa had put up the posters, which slogans that read "With your victory, Assad will vanish", ahead of an event in support of the Syrian revolution, the source added.

The group has now released a statement denouncing the Ba'ath Party's action.

"While we are careful not to incite tensions in our city, we affirm everyone's freedom to express their position, views and ideas within the law as guaranteed by the constitution, away from the methods [adopted by the Shabbiha] and intimidation that do not shake our resolve," the statement said.

Heightened Tensions and Violence

Violence continued across Syria despite the president's claims to have accepted UN-Arab League envoy Kofi Annan's six-point plan to end the bloodshed.

Shelling and fighting continued in several towns, including Homs and Deraa, according to activists.

The Britain-based Syrian Observatory for Human Rights also said the army started a "major operation" in Douma, a suburb of Damascus, with tanks shelling the area while troops continued to clash with defectors, who have joined the Free Syria Army.

Amnesty International said it had counted 232 deaths since Syria accepted Annan's peace plan last week, increasing doubts over whether Assad is actually committed to ending the violence.

Turkey has reported that more than 1,600 Syrians have crossed the border due to the increased fighting over the last two days, putting the total number of Syrian refugees in the country taking sheltering from the fighting to more than 20,000.

Annan's UN envoy arrived in Damascus to discuss implementing the ceasefire plan.

A spokesperson for Annan said Syria had reported withdrawing some troops, adding that the UN expects a full ceasefire to take effect by 12 April.

Annan had previously set 10 April as the deadline for the ceasefire plan to be fully implemented.