Rebel shelling of government-held areas in Aleppo kills and wounds dozens on eve of elections

A Syrian official and activists say dozens of people have been killed or wounded over the past three days in stepped-up rebel attacks on government-held areas in the northern city of Aleppo.

The attacks are the latest ahead of the country's presidential election on Tuesday, a highly contentious vote amid a civil war that has killed more than 160,000 people.

The Syrian opposition and its Western allies have denounced the balloting as a sham. President Bashar Assad is widely expected to win a third seven-year term.

The Britain-based Syrian Observatory for Human Rights said on Monday that 50 people have been killed in Aleppo since Saturday. Syria's Information Minister Omran al-Zoubi said 20 people were killed on Saturday alone.

Rebels have threatened to disrupt the voting in opposition-held areas.