Explosions have struck two cities in Syria, killing several people a day after a spokesman for Kofi Annan, the UN-Arab League envoy, said the UN peace plan for Syria remained on track.

The UK-based Syrian Observatory for Human Rights reported that five people were killed on Saturday in a blast in the Tala Azaziya neighbourhood of Aleppo apparently targeting a car wash.

A Free Syrian Army member told Reuters that the opposition group had targeted the car wash because it was used by members of pro-government armed gangs and said he had seen seven bodies at the scene.

Al Jazeera’s Anita McNaught, reporting from Mardin in Turkey, said: "The attack on the car wash, according to Free Syrian Army sources, was a revenge attack because it was a car wash used by Shabiha, a paramilitary militia that the government deploys.

"A lot is happening in Aleppo, a city that is beginning to see almost daily protests against the government. A city that was slow to rise up."

Syria's state news agency said three people had been killed in a blast in the city.

Crater in the street

Earlier, a bomb attached to a military vehicle on the central Damascus highway of Sharia al-Thawra caused destruction to nearby cars and buildings, but there were no reports of casualties.

Spotlight In-depth coverage of escalating violence across Syria

The blast shook the neighbourhood near a military food co-operative, destroying nine cars and leaving a crater in the street, according to a reporter from The Associated Press news agency who visited the scene.

No one immediately claimed responsibility for the blasts.

On Friday, Ahmad Fawzi, Annan's spokesman, told a UN briefing in Geneva that the peace plan remained on track and said Syria's more than year-long crisis would not be resolved "in a day or a week".

The plan aims at ending the violence, bringing in relief supplies, releasing detainees and forging a political process to address grievances in Syria.

His comments came as the Local Co-ordination Committees, an opposition activist network, announced the deaths of 33 people in renewed violence across the country. Massive anti-government protests were also reported on Friday.

In the central city of Hama, government forces used gunfire to disperse protesters in two districts of the city and in another town of the same province, activists reported.