The Syrian government has called on the exiled opposition to return home to participate in a national dialogue to end the 22-month conflict, as the rebels intensified attacks on a security branch and checkpoints in the countryside of the capital Damascus.

In a statement issued Thursday evening, Syria's Interior Ministry said the exiled opposition and other Syrians who have fled the country legally or illegally are permitted to come back through certain border points, adding that they would be provided with all facilitation, including the freedom to leave or stay in the country.

The announcement has come in coordination with the Ministry of National Reconciliation, the statement said.

The invitation to the exiled opposition came on the bases of recent proposals by President Bashar al-Assad, who has also talked about a ceasefire and the establishment of a broad-based government and parliament.

Syria's exiled opposition rejected any dialogue even from the very first months of the conflict. The various opposition factions, recently gathered under one umbrella, dismissed Assad's new vision for political solution and set his ouster as a prelude to any solution.

The friendly gesture on the government side was answered by intense fighting and explosions that have rocked several areas in the conflict-torn country.

An overnight blast rocked the suburb of Sa'sa near the capital Damascus on Thursday, leaving undisclosed number of causalities, the state-TV said, stopping short of giving further details.

But an online news website said that two suicide car bombs ripped through a checkpoint and the branch of military security in that area, adding that the second car was rigged with two tons of explosives.

The activists' network, Local Coordination Committees also confirmed the rebels Free Syrian Army blasted the military security branch in Sa'sa area and attacked a checkpoint there as well.

The deadly twin blast was not the only one that rattled the capital overnight, as an explosive device went off in al-Qaimaria area in the old quarter of Damascus, injuring two people, according to local media reports.

Also on Thursday, bomb squads defused an improvised explosive device planted near a park in the Christian-dominated Bab Touma area of Damascus, reports said.

On the opposition side, the Britain-based Syrian Observatory for Human Rights said an explosion rocked the Damascus' district of Barzeh late on Thursday.

The group gave no details on human losses but said the blast was caused by an explosive device that ripped through a parked Mercedes in that area.

It was not immediately clear what the target of the explosion was.

The Observatory, meanwhile, said that five civilians, including two women and three men, were gunned down in the Damascus' countryside of Tishreen, adding that pro-government gunmen were behind the killing.

Activists also reported heavy shelling on rebel strongholds in eastern and southern rims of Damascus and elsewhere in the war-engulfed country on Thursday, putting the death toll on Thursday at 116.

Still, the account could not be independently confirmed.

As the violence keeps grinding on, Syria's Minister of Endowment Mohammed Abdel Sattar called for "million-man prayers" to be held on Friday for the peace of Syria and on the occasion of the birthday of Islam Prophet Mohammad.

The prayers will be held at Syria's mosques nationwide on Friday to appeal for the re-establishment of security in the country, which has been gripped by a prolonged crisis that has killed more than 60,000 people, according to a recent UN tally.

Earlier in the day, President al-Assad attended special prayers at a Damascus mosque to mark the prophet's birthday.