UN-Arab League envoy Lakhdar Brahimi on Sunday kept up his push for peace talks on Syria, where a suicide car bombing and assault on a Damascus checkpoint killed 16 soldiers.
Brahimi, the joint envoy of the UN and the Arab League, was to meet the head of the pan-Arab bloc in Cairo before heading for talks in Damascus and a visit to its key regional ally Iran.
After talks with Egypt's foreign minister on Saturday, he said "intense efforts" were under way to convene a Syria peace conference in Geneva next month.
But despite strong backing from Russia and the United States, prospects for the planned conference remain dim, with Syria's opposition divided and due to vote next week on whether to take part.
The opposition is adamant that President Bashar al-Assad must agree to step down before it will join any talks, a demand that is unacceptable to Damascus.
The main National Coalition opposition bloc said members will decide next week whether to attend the Geneva talks, while the Syrian National Council, a key coalition member, has threatened to quit if they do.
The push for the Geneva talks will also be high on the agenda of US Secretary of State John Kerry, who heads to Europe to attend a "Friends of Syria" meeting in Britain on Tuesday which will also be joined by opposition representatives.
The renewed push for peace talks comes after Damascus accepted in September a US-Russian deal to hand over its chemical arsenal for destruction.
But the political opposition remains divided amid recent clashes between mainstream rebels and jihadists, as well as growing rifts between fighters on the ground and the external opposition.
Syrian state media blamed "terrorists" for a bombing at the entrance to the Damascus suburb of Jaramana, a mixed Christian-Druze district suspected by Sunni hardliners of sympathy for the regime and hit by several previous deadly blasts.
The Syrian Observatory for Human Rights said a suicide bomber from the Al-Qaeda-linked Al-Nusra Front detonated an explosives-packed car at the checkpoint between Jaramana and rebel-held Mleha.
Fighting raged for much of Saturday, with rebel mortar fire hitting Jaramana and regime aircraft striking back, according to the Britain-based Observatory, which relies on activists and medics on the ground.
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At least 16 soldiers and 15 jihadists were killed, it said.
One resident said the ferocity of the fighting in the area was "unprecedented" since Syria's conflict erupted in March 2011, telling AFP by telephone: "It's very intense. We can hear automatic weapons fire, mortar rounds, bombardments."
UN humanitarian chief Valerie Amos called on Saturday for a ceasefire in another embattled Damascus suburb, Moadamiyet al-Sham, where thousands of people were evacuated last week and where she said "the same number or more remain trapped."
The southwestern district was one of a number of suburbs hit in an August 21 sarin gas attack, blamed by the opposition on the regime, which led to the deal to dismantle Syria's chemical arsenal.
In sign of the quickening collapse of Syria's health care system, the World Health Organisation said it had detected two possible cases of polio in Deir Ezzor province in the east, which, if confirmed, would be the country's first known cases since 1999.
Fighting raged around Deir Ezzor city early Sunday. Activists of the Syrian Revolution Coordinators' Union reported four air strikes on rebel-held areas of the provincial capital.
In the north, the air force carried out new strikes on rebel fighters around Aleppo central prison, which they trying to wrest from government control, the Observatory said.
Inmates issued "calls to the Red Crescent to bring food into the jail, after a prisoner died on Saturday as a result of acute malnutrition".
Meanwhile, nine Lebanese Shiite pilgrims seized by Syrian rebels 17 months ago and two Turkish Airlines pilots kidnapped in Beirut in August arrived back home late Saturday under an exchange deal mediated by Turkey and Qatar.
The nine pilgrims, who were kidnapped by Syrian rebels last year as they were returning from visiting Shiite holy sites in Iran, were welcomed home in Beirut late on Saturday.
The Turkish pilots, seized in Lebanon to put pressure on opposition supporter Turkey to persuade the rebels to release the pilgrims, were freed and flown home to Istanbul.
Syrian rebels had also demanded the release of some 200 prisoners from Syrian jails in exchange for freeing the pilgrims. It was not clear if those releases went ahead.