Syrian rebels clashed with regime troops in Damascus and second city Aleppo on Monday as the opposition held makeover talks in Qatar and diplomatic efforts to end the violence spun their wheels.
The fresh clashes came as the rebels sought to keep momentum after seizing a major oilfield and shooting down a warplane in the eastern province of Deir Ezzor on Sunday.
Fighting had erupted Sunday night in southern districts of the capital on the periphery of the Yarmuk Palestinian camp, and renewed at dawn on Monday, said the Syrian Observatory for Human Rights, a Britain-based watchdog.
It said Palestinian fighters had joined the clashes on both sides.
In Aleppo, fighting broke out at a roundabout at the northwest entrance to the city in the Zahraa district and on the airport road to the southeast, the Observatory and residents said. One resident of a district near Zahraa said Monday's fighting in the area was the heaviest in recent days.
"It's been almost one week that we are living in terror at night. We hear everything -- gun battles, tank shelling, explosions... The clashes before dawn today were the worst all week," Samir, a 37-year-old pharmacist, told AFP.
A source with the Syrian Arab Red Crescent also said Monday its main warehouse in Aleppo had burned down amid recent fighting, with the loss of crucial supplies including medicine, food and winter relief items like blankets.
The rebels have scored significant wins in recent weeks and hold swathes of territory in the country's north, but have struggled to gain ground in and around Damascus and in the commercial hub Aleppo amid heavy bombardment from regime air power.
Strikes from regime warplanes and helicopter gunships have reached a new level of intensity in recent days as government forces try to reverse rebel gains on the ground.
Air raids continued Monday with jets hitting the eastern outskirts of Damascus, the northwest province of Idlib and near the Iraqi border in the east, the Observatory said. It said that 203 people, including 112 civilians, were killed in nationwide violence on Sunday.
The escalating conflict has added urgency to a meeting of the Syrian National Council in Qatar, where the United States is reportedly pressing for a new umbrella organisation to unite the country's fractured opposition.
According to the reports, which emerged after US Secretary of State Hillary Clinton said the SNC was not representative, long-time dissident Riad Seif is touted as the potential head of a new government-in-exile dubbed the Syrian National Initiative.
But as the Doha meeting began Sunday, Seif denied planning to head such a government. "I shall not be a candidate to lead a government in exile... I am 66 and have health problems," he told reporters.
SNC chief Abdel Basset Sayda denounced what he called "efforts to bypass the SNC and numerous attempts to find substitutes" for the group, though he recognised that some criticisms of it are founded.
The SNC lashed out on Friday at alleged US interference, accusing Washington of undermining the revolt and "sowing the seeds of division" by seeking its overhaul.
On the diplomatic front, Russian Foreign Minister Sergei Lavrov met in Cairo on Sunday with Arab League chief Nabil al-Arabi for talks on Syria, but the meeting proved fruitless. "We discussed the situation in Syria... reviewing what has been done so far and if there is any way to move forward. And let us be clear, there wasn't any agreement on anything," Arabi told a joint news conference.
Lavrov stressed the need to "convince the Syrian parties to cease fire and sit down for negotiations in accordance with the Geneva agreement," referring to a Russian-backed transition plan world powers agreed on June 30.
Russia and China have stymied Western- and Arab-backed efforts to put more pressure on President Bashar al-Assad's regime by blocking UN Security Council resolutions.
The Observatory says more than 36,000 people have died since the uprising against Assad's rule broke out in March 2011, first as a protest movement inspired by the Arab Spring and then as an armed rebellion.