Syrian rebels seized a crossing on the Turkish border Wednesday even as they quit a swathe of south Damascus that activists said had been reduced to a disaster area by weeks of heavy fighting.
UN chief Ban Ki-moon said it was "troubling" that 18 months into the uprising against President Bashar al-Assad's rule both sides seemed determined to battle on to the bitter end.
The new UN envoy on children in conflict Leila Zerrougui said the world body was investigating Syrian rebel groups as well as government forces for attacks targeting children.
Assad told the visiting foreign minister of key ally Iran that the uprising targeted both their governments and their allies across the region.
The Tall al-Abyad border crossing which the rebels seized was the fourth they have captured on the border with Turkey.
Turkish media footage showed rebel fighters pulling down the regime flag at crossing on the main highway between the city of Raqa in northeastern Syria and the Turkish city of Sanliurfa.
Turkey's Anatolia news agency reported that the rebels tore down Assad's pictures to celebrate the capture but an opposition activist in Raqa said that fighting was still raging in the area as government troops attempted to recapture the crossing.
The activist, who gave his name only as Abu Assaf, told AFP by telephone that the rebels had raised the flag of the Free Syrian Army after inflicting heavy casualties on government troops.
"The fighters have taken over all the security and government buildings in the crossing, and they have raised the FSA flag," Abu Assaf said.
"Many army troops surrendered, and many others were injured," the activist said.
The mayor of Akcakale district on the Turkish side of the border, Emre Akgun, told NTV television that stray bullets fired from the Syrian border post had hit houses inside Turkey and wounded three civilians.
Meanwhile, rebels withdrew from three southern districts of Damascus after weeks of heavy combat and shelling, while the army bombarded districts oF the city and adjacent areas, the Syrian Observatory for Human Rights said.
The bodies of 11 people were found in the Jobar district of Damascus, some of them belonging to people who had been detained by security forces, the Observatory said, adding that nationwide at least 68 people were killed in violence on Wednesday, 50 of them civilians.
A network of activists, the Syrian Revolution General Commission (SRGC), described as "disaster areas" the Al-Hajar al-Aswad, Qadam and Assali districts, and the Yarmuk Palestinian refugee camp.
-- 'Military means not the answer' --
The UN chief said he found it "troubling" that both Assad and Syrian opposition seemed determined to fight to the end, but renewed appeals for political dialogue.
"Unfortunately both sides, government and opposition forces seem to be determined to see the end by military means," Ban told a news conference.
"I think military means will not bring an answer," he added calling for "political dialogue reflecting the genuine aspirations and will" of the Syrian people.
Ban said that UN-Arab League envoy Lakhdar Brahimi, who just wrapped up his first visit to Syria and its neighbours since taking up his post earlier this month, may put a plan to Assad's government after talks at UN headquarters in New York next week.
The new UN envoy on children in conflict Leila Zerrougui said the world body was investigating reports that Syrian rebels may have carried out attacks that had killed children and may also have used children in their operations.
"We have received information concerning indiscriminate bomb attacks which have killed children in Damascus and other areas, and continue to document incidents committed by armed actors, such as the Syrian Free Army, who may have children associated with their forces," Zerrougui said.
She told the UN Security Council that UN agencies had "documented government attacks on schools, children denied access to hospitals, girls and boys suffering and dying in bombardments of their neighborhoods and also being subject to torture, including sexual violence."
Russia's deputy ambassador Sergey Karev complained that the last UN report "accuses only government forces and their backers of crimes against children in Syria" and that "crimes perpetrated by opposition members are only mentioned in passing."
Russia and China -- both traditional Damascus allies -- joined Pakistan and Azerbaijan in refusing to back a normally routine Security Council resolution backing the envoy's work.
Iranian Foreign Minister Ali Akbar Salehi called for a Syrian solution to the conflict as he visited Damascus for talks with Assad.
Assad said the war engulfing Syria was targeting not only it but the "axis of resistance," a term Syria, Iran and Lebanon's Shiite movement Hezbollah use to refer to their common opposition to Israel.
Salehi said the country was "facing a problem, and we hope that this problem can be solved as soon as possible."
But he added that "Syria has very strong, solid ties with Iran, especially at the political level."
The former head of Syria's chemical arsenal, Major General Adnan Sillu, was quoted by British newspaper The Times as saying he believed the regime would eventually use those weapons against civilians.
The Times quoted Sillu as saying that before his defection three months ago he had been involved in "serious discussion about the use of chemical weapons, including how we would use them and in what areas."