BEIRUT -- Syrian government forces bombed rebel positions from the ground and air in the northern city of Aleppo on Friday as protesters across the country appealed for anti-aircraft guns for opposition fighters to offset the regime's increasing use of aerial attacks.
The relentless violence triggered a fresh wave of civilians streaming across the border into neighboring Turkey to escape the civil war in their country. In New York, U.N. diplomats said the search was on for another envoy to replace Kofi Annan who gave up trying to broker peace in Syria.
The diplomats said former Algerian foreign affairs minister and longtime U.N. official Lakhdar Brahimi is a strong candidate to take over from Annan, who is leaving by the end of the month. The diplomats spoke on condition of anonymity because they were not authorized to speak to the media.
Annan, a former U.N. chief, announced his resignation last week as joint U.N.-Arab League envoy to Syria, ending a frustrating six-month effort that failed to achieve even a temporary cease-fire as the conflict in the country descended into a full-out civil war.
The search for Annan's replacement suggested the international community was not entirely giving up on diplomacy to try end the conflict that has claimed the lives of at least 20,000 people, according to human rights activists.
Rebels and activists in Aleppo said they have had enough of diplomacy and appealed Friday for weapons from the international community.
"The warplanes and helicopters are killing us, they're up there in the sky 15 hours a day," said Mohammad al-Hassan, an activist in Aleppo's main rebel stronghold of Salaheddine.
"It's warplanes against Kalashnikovs, tanks fighting against rifles," he said. "I don't know how long this situation can be sustained."
The regime has been trying to drive rebels out of Aleppo, Syria's largest city, for more than two weeks. But the blistering attacks on rebel positions from the ground and air appear to be only slowly chipping away at the opposition's grip on its strongholds.
The state news agency claimed Wednesday that Assad's force had regained control of the Salaheddine neighborhood, the main rebel area in Aleppo. But activists said rebels were still putting up a fight there on Friday despite being low on ammunition.
Aleppo holds great symbolic and strategic importance. Some 25 miles (40 kilometers) from the Turkish border, it has been a pillar of regime support during the uprising against Syrian President Bashar Assad's regime. An opposition victory there would allow easier access for weapons and fighters from Turkey, where many rebels are based.
An Aleppo-based activist who goes by the name of Abu Issa said government forces were shelling rebel-controlled areas in the southwestern part of Aleppo and in the northeast. Towns and villages in Aleppo suburbs were "at the mercy" of fighter jets and helicopters strafing the area, he said.
"Soon there will be nothing left to destroy in Aleppo ... The regime is using air power without shame," said Abu Issa, who was not using his real name for fear for his own safety.
Protesters across many parts of the country rallied after midday prayers Friday, urging the international community to arm the opposition fighters.
"Give us with anti-aircraft guns. Where is your conscience?" read a small poster held by a protester in the village of Kfar Zeita in the central Hama province.
Underscoring the world community's reluctance to arm the fighters -- a loosely linked group of rebel forces and army defectors -- Britain's government said Friday it is giving an extra 5 million pounds (US$7.8 million) worth of aid to Syria's opposition but no weapons.
Foreign Secretary William Hague said the funds would pay for items including satellite phones, power generators and medical kits. He said diplomats would also intensify contacts with the political wing of the Free Syrian Army as concern grows over the country's possible fate if President Bashar Assad's regime is deposed.
Britain has previously given 1.4 million pounds (US$2.2 million) worth of nonlethal support to Syria's opposition. The United States has earmarked a fund of $25 million to spend on nonlethal communications assistance.
Turkish officials said more than 1,500 Syrians arrived over the past 24 hours, increasing the number of refugees in Turkey to about 51,500.
The activists with the Observatory and the Local Coordination Committees also reported shelling Friday of several areas just outside Damascus, where rebels also were active. Residents reported hearing loud blasts in Damascus from the shelling on the outer edges of the city, according to the activists.
Syrian troops say they have purged the rebels from the capital after intense, weeklong battles last month. But opposition fighters continue to stage hit-and-run attacks and are active in the suburbs around the city.