A spate of car bombs tore through the heart of Aleppo on Wednesday, killing at least 27 people and wounding 72, officials said, in the latest wave of violence to engulf Syria's battered commercial capital.
The bombings were the deadliest in Syria's raging civil war since August 28, when a car bomb targeted the funeral of two government loyalists in a Damascus suburb, also killing 27 people.
Three car bombs exploded early on Wednesday around Aleppo's Saadallah al-Jabiri Square near a military officers' club and a hotel, the Syrian Observatory for Human Rights said, which reported that "many soldiers" were among the dead and wounded.
A city official, speaking on condition of anonymity, gave an initial toll of 27 dead and 72 hurt but said the toll could rise "because many people were badly injured."
State television reported "three terrorist explosions" in the city and broadcast scenes of massive destruction of buildings in the square.
An AFP correspondent reported hearing loud blasts, which caused huge plumes of smoke to billow across the city.
The facade of the hotel was destroyed and a cafe collapsed. One person emerged from the hotel with his face covered in blood, the correspondent said.
All government buildings were immediately closed after the blast.
Aleppo, with a population of 1.7 million people, has been since mid-July one of the focal points of the conflict roiling the country.
Several districts of Aleppo were also bombed on Tuesday, the Observatory said, while pro-regime daily Al-Watan reported that extra troops were being sent to Aleppo.
"New reinforcements have arrived to support the army... and the armed men (rebels) are now fatigued and have begun to flee to their villages and towns in the province of Aleppo and elsewhere," it said in a report on Tuesday.
Fighting at the weekend rocked the centuries-old UNESCO-listed souk in the heart of Aleppo and sparked a fire that damaged hundreds of shops.
Bombings are increasingly becoming part of the unrest, which began in March last year as peaceful protests for reform but has since morphed into an armed insurgency, with more than 31,000 people killed, according to activists.
A suicide car bomber struck a security force headquarters in the Kurdish city of Qamishli on Sunday, and four troops guarding the military headquarters in Damascus were killed last Wednesday when twin blasts blamed on suicide bombers targeted the building.
On July 18, rebels carried out a massive bombing on a complex in Damascus, killing four security chiefs, including Assad's brother-in-law and the defence minister.
Regime forces have since pushed the rebels to the outskirts of the capital, but they have lost control of several border crossings and are battling to retake Aleppo.
Nationwide, at least 104 people were killed on Tuesday -- 57 civilians, 26 soldiers and 21 rebels, the Observatory said.
Among them were civilians hit by intense shelling from the army against rebel-held areas of Damascus.
Syria peace envoy Lakhdar Brahimi is due back in the region this week to try to revive talks aimed at ending the bloodshed, officials said.
Jan Eliasson, deputy to the UN chief, said he did not know if Brahimi would be able to enter Syria, but hoped to persuade the Assad regime to "go in the direction of a reduction of violence."
In Lebanon, Damascus-ally Hezbollah reported that one of its senior commanders had been buried after having been killed "while performing his jihadist duties."
A Syrian rebel commander in the central province of Homs who identified himself only as Abu Moayed told AFP the commander and two of his escorts had been killed by a home-made landmine near Qusayr," a rebel-held, besieged town in the province.
Hezbollah is one of Lebanon's main political parties and its militia is the country's most powerful military force.
Meanwhile, the UN refugee agency said the number of Syrian refugees in neighbouring countries has more than tripled since June to over 300,000, and that number is expected to more than double again by year-end.