International peace envoy Lakhdar Brahimi arrived in Cairo Sunday on his first trip to the region as Moscow and Washington aired their differences over Syria and violence there claimed yet more lives.
Troops shelled several districts of the northern city of Aleppo and clashed with rebels as other regions were bombarded in a new day of violence that killed at least 88 people, the Syrian Observatory for Human Rights reported.
Observatory chief Rami Abdel Rahman said the overall death toll from 18 months of violence in Syria has now risen to more than 27,000.
Seventeen people were also killed and more than 40 wounded in a "terrorist attack" in the stadium area of Aleppo, the official SANA news agency reported.
A bomb targeting a bus carrying civilians and soldiers killed four people and wounded dozens in central Syria, the Observatory said, as the opposition announced that a vocal anti-regime film-maker had been killed in Aleppo.
Brahimi, who has said he was "scared" of the task ahead, arrived in Cairo ahead of talks on Monday with Arab League officials, Egypt's President Mohamed Morsi and other leaders as he finalises plans for a visit to Damascus.
His spokesman Ahmad Fawzi said the date of Brahimi's visit to Syria will be fixed once the final details of his programme are set.
The veteran troubleshooter, who succeeds ex-UN and Arab League envoy Kofi Annan who quit in frustration at UN Security Council divisions on the conflict, has described the bloodshed as "staggering" and called the destruction "catastrophic."
Brahimi wants guarantees he will get a proper meeting with President Bashar al-Assad before he goes to Damascus, diplomats said, but with no signs of the violence ending, expectations are low he will have any more success than Annan.
Iran's Mehr news agency quoted an official as saying Brahimi was also contemplating visiting Tehran -- Syria's diehard ally -- after Damascus.
Annan also visited the Islamic republic in an effort to get it involved in resolving the conflict, but Washington has accused Tehran of playing a "nefarious" role in Syria.
US Secretary of State Hillary Clinton said on Sunday that a new Security Council resolution on Syria would be pointless if it had "no teeth," because Assad would just ignore it.
Speaking in Russia, Clinton said she was willing to work with Moscow on a new resolution, but warned Washington would step up support to end Assad's regime if the measure did not carry consequences.
"There is no point to passing a resolution with no teeth because we've seen time and time again that Assad will ignore it and keep attacking his own people," she said.
Russian Foreign Minister Sergei Lavrov said on Saturday after meeting Clinton that he hoped to seek Security Council approval for a peace plan agreed in June in Geneva that called for a ceasefire and political transition.
-- Pitched battles in Aleppo --
Clinton said she hoped for progress but was "realistic" over US differences with Russia on Syria.
If those differences persist, "then we will work with like-minded states to support a Syrian opposition to hasten the day when Assad falls," she said.
Washington has said it is providing non-lethal assistance to the opposition in Syria, whose regime has been a Moscow ally since the Cold War.
On the ground, troops and rebels fought pitched battles in Aleppo as each side tried to gain more territory in Syria's battered economic hub, activists and the Observatory said.
The watchdog said at least two people were killed when mortar rounds struck a residential building as fighting raged in Hanano district, where troops on Saturday repelled an offensive by rebels seeking control of an army barracks.
Fierce clashes also shook the outskirts of Midan, as rebels entrenched in the nearby Bustan al-Basha stronghold tried to seize the neighbourhood controlled by regime forces.
"The bombardment of Bustan al-Basha has stopped but could start up again any time," one resident told AFP.
A main water pipe was destroyed, either by air strikes or the fighting, and residents reported water shortages.
SANA on Sunday reported: "A terrorist attack in the municipal stadium district near Al-Haya hospital and Aleppo central hospital killed 17 people and wounded 40, according to a preliminary toll."
In the central province of Homs, a bomb attack on a bus carrying civilians and soldiers killed at least four people, reports said.
"Four people were killed and others wounded in an explosion by a bomb which was planted by a terrorist group in a bus on the route from Homs to Messyaf," state television said.
The Observatory said there were two explosions.
"We know for sure that four people were killed but we don't know if they were civilians or military," Abdel Rahman told AFP.
"It was a large bus and there are dozens of casualties."
In Damascus, troops bombarded the southeastern district of Tadamun and nearby Al-Hajar al-Aswad, with clashes also reported at the Yarmuk Palestinian camp, the Observatory said.
Late on Sunday the UN Relief and Works Agency for Palestinian refugees said one of its staffers was killed by a bullet to his chest in the Yarmuk area.
The opposition Syrian National Council also announced the death of film-maker and journalist Tamer al-Awam, 34, on the front lines of Aleppo "by the bullets of the murderous and treacherous regime."
A Syrian website, Syrian Documents, said Awam was killed on Saturday while shooting a film for the rebel Free Syrian Army.