Syrian rebels shelled a key area of Damascus home to President Bashar al-Assad's Alawite minority, embassies and government buildings on Wednesday, as they stepped up attacks on his power base.
Britain, meanwhile, said it was to open talks with the rebels in a bid to help end the violence, as the main opposition Syrian National Council said it hoped resolving the conflict would top re-elected US President Barack Obama's agenda.
The shelling of the mainly Alawite Mazzeh 86 district came a day after a car bomb hit another Alawite area in the suburb of Qudsaya, as rebels increasingly target Assad's supporters in the minority, an offshoot of Shiite Islam.
Sectarian divides are a key factor in Syria's armed rebellion, with many in the Sunni Muslim majority frustrated at more than 40 years of Alawite-dominated rule.
State news agency SANA reported that shelling had hit a home and mini-bus carrying passengers in Mazzeh 86, which lies beneath Assad's hilltop presidential palace, killing at least three civilians.
The Syrian Observatory for Human Rights, a Britain-based watchdog that relies on a network of activists and medics on the ground, confirmed the shelling and said at least three civilians were killed and 12 wounded.
It previously reported a car bombing in an Alawite area of the suburb of Qudsaya on Tuesday that killed 19 people and another on Monday in Mazzeh that left 13 dead.
"The attacks on Mazzeh are a significant turning point because for the first time the Alawite community, which has never been targeted as such, is directly associated with the regime and targeted for this," said Fabrice Balanche, an analyst with the Mediterranean and Middle East Studies and Research Group in Paris.
Rebels also clashed with pro-regime Palestinian forces in the southern Al-Hajar al-Aswad district and the nearby Palestinian refugee camp of Yarmuk, the Observatory said, as the area becomes another focal point of violence.
Pro-regime newspaper Al-Watan said troops had launched an offensive on the Tadamun district near the camp to "liberate civilians and hostages" held by the rebel Free Syrian Army (FSA) and protect the Palestinians.
A car bomb exploded overnight in the southern Qadam neighbourhood, causing at least one death, after violence on Tuesday left a total of 150 dead, including 79 civilians, the Observatory said.
-- Britain to contact rebels --
Fighting raged and air strikes hit in other parts of the country, while SANA reported that a judge was killed when a car bomb exploded outside his home in the northeast of Damascus.
In a preliminary toll, the Observatory said at least 22 people had been killed on Wednesday.
British Prime Minister David Cameron's office said the government had authorised officials to have contacts with military representatives of the opposition, although government sources stressed the initiative was about political dialogue, not providing weapons.
British officials said they would make clear to the Syrian groups that they must respect human rights, after a video last week purported to show rebels beating and executing pro-regime fighters.
Cameron himself toured a desert refugee camp for Syrians in northern Jordan on Wednesday.
"I am hearing appalling stories about what has happened inside Syria so one of the first things I want to talk to Barack about is how we must do more to try and solve this crisis," he said.
As the Syrian National Council met in the Qatari capital Doha, leading members said Obama should work to end the crisis following his re-election.
SNC chief Abdel Basset Sayda told AFP he hopes the US administration would now "address the Syrian crisis with seriousness and responsibility in order to end the massacres and destruction."
Washington has voiced increasing frustration with the SNC for not fully representing the opposition, and the talks in Qatar will see an initiative put forward to form a new government-in-exile to represent the opposition.
The Observatory says more than 36,000 people have died since the uprising against Assad's regime erupted in March 2011, first as a protest movement and then an armed rebellion after repression.
Pope Benedict XVI called for peace in Syria on Wednesday, but admitted that a planned visit by a Vatican delegation to the conflict-torn country would not go ahead because of conditions there.
Circumstances in Syria "have not rendered possible" the visit, the pope said at his weekly general audience in St Peter's Square, adding that he had dispatched an envoy, Cardinal Robert Sarah, to Lebanon to discuss the crisis.