Fierce fighting around Syria's contested northern province of Aleppo killed at least 21 rebels on Monday as rockets slammed into a government-held district in the provincial capital, killing nine people.
The Britain-based Syrian Observatory for Human Rights said that along with the 21 rebels, at least 30 soldiers were killed or wounded in Monday's clashes in the province.
President Bashar Assad's forces, backed by Lebanese Hezbollah militants and pro-government militias, have been trying to wrest as much territory in Aleppo from the opposition ahead of the June 3 presidential elections.
In the city of Aleppo, Syria's largest and the provincial capital, government forces have been relentlessly shelling opposition districts with aircraft and artillery in recent months.
Aleppo has been divided between government- and opposition-held areas since rebels launched an offensive there in mid-2012, capturing whole neighborhoods and large sections of territory outside the city and along the border with Turkey.
The rebels have been striking back, firing mortars and makeshift rockets into cities and towns under control of Assad's forces. They have also detonated several car bombs in major cities, including in the capital, Damascus.
The state-run SANA news agency said rockets struck in Aleppo's residential neighborhood of Ashrafiyeh overnight, killing nine people and wounding several, mostly women and children.
The Observatory said troops loyal to Assad were battling Islamic rebel groups, including the al-Qaida-linked Nusra Front, around two rebel-held villages in Aleppo province Monday.
The clashes, which erupted after midnight Sunday, killed at least 21 rebels, and killed or wounded about 30 Syrian soldiers, said the Observatory, which has documented the 3-year-old conflict based on reports from a network of activists on the ground. Syrian government does not publicize its casualties in the war.
Syria's conflict, which began with largely peaceful protests in March 2011, has evolved into a civil war with sectarian overtones, pitting predominantly Sunni Muslim rebels against the Assad' government that is dominated by Alawites, a sect in Shiite Islam. More than 150,000 people have been killed and millions have been displaced by the war.
Islamic extremists, including foreign fighters and Syrian rebels who have taken up hard-line al-Qaida-style ideologies, have an increasingly prominent role in the war, dampening the West's support for the rebellion to overthrow Assad. Many Syrians, particularly religious minorities, have also come to doubt the opposition, fearing that Islamic radicals would take over if Assad is ousted.
Assad took power after the death of his father, Hafez, in 2000. He has maintained throughout the conflict that his government is facing an uprising, insisting that his army is fighting terrorists that are part of the Western- and Gulf Arab-sponsored plot to destroy Syria.
Over the past year, Assad's forces have been taking back rebel-held areas throughout Syria with a mix of crippling blockades, deals with rebels and relentless pounding of opposition-held areas. Presenting himself as a defender of united and religiously mixed Syria, Assad has pushed for the June 3 vote to seek a third seven-year term amid fierce fighting.
Despite two other candidates on the ballot, Assad is widely expected to win the vote, which opposition activists and Western countries have condemned as a sham. The vote is expected to be held only in government-controlled territory.