Beirut: An air strike on a school in Syria`s northern city of Aleppo by President Bashar al-Assad`s forces killed at least 18 people on Wednesday, mainly children, a day after attacks on government-controlled cities killed more than 100 people, activists said.
The devastating strikes, which stand out for their ferocity even in a civil war which now kills between 200 and 300 people a day, come as Syria prepares for an election likely to extend Assad`s grip on power.
On Tuesday, a day after Assad nominated himself to run for a third term in a vote already derided as a sham by his opponents, two car bombs struck in a government-controlled part of Homs.
The Syrian Observatory for Human Rights monitoring group said on Wednesday the death toll from those bombs had risen to 100. A mortar attack on a school, which authorities blamed on "terrorists" battling Assad, also killed at least 14 people.
Wednesday`s air strike on the Ain Jalout school in the Al-Ansari district of Aleppo appeared to be part of the sustained bombardment of the contested northern city by Assad`s forces.
Pictures from the school showed blood on corridor walls and debris in classrooms, while video footage released by activists at the anti-Assad Aleppo Media Centre showed more than a dozen bodies which appeared to be children laid out on a tiled floor.
The Observatory put the death toll from the attack at 18, while the Aleppo Media Centre said 25 children had been killed. 
For months Assad`s forces have dropped barrel bombs - crude but powerful explosives which are not designed for precision targeting - on rebel-held parts of the city, despite an appeal from the U.N. Security Council two months ago for a halt.
The U.S.-based Human Rights Watch said this week it had documented 85 sites in Aleppo hit by aerial bombardment since the Security Council`s appeal.
More than 150,000 people have been killed in Syria`s three-year-old conflict which grew out of protests against Assad`s rule in March 2011. The United Nations says 6 million people have been displaced in Syria and another 2.5 million refugees have fled abroad. Forces loyal to Assad, who is expected to face only a token challenge in the June 3 election, have been consolidating their hold around Damascus and the centre of the country, backed by Iraq Shi`ite fighters and Lebanon`s Hezbollah, But the mainly Sunni Muslim rebels and foreign jihadis have pushed his troops out of swathes of northern Syria and the oil-producing and agricultural east of the country.