Explosions rocked Syria's northern city of Aleppo on Friday, killing some soldiers and civilians, Syrian state television and activists said.

State television reported two terrorist explosions in the city. They targeted a branch of military intelligence and a security force base, it said.

Civilians and military personnel had been killed and wounded, it said, but gave no figures.

The opposition Syrian Observatory for Human Rights quoted residents as saying three blasts occurred, including one near a security forces' building in the city. They also reported hearing gunfire.

A resident contacted by Reuters said an area around a military intelligence complex in the New Aleppo district had been sealed off after the explosions.

Aleppo, Syria's main commercial hub, had been relatively quiet during the 11-month uprising against President Bashar al-Assad but has seen increasing protests and violence in recent weeks.

On December 23, suicide car bombers struck Damascus in what was then the bloodiest violence in the capital since the revolt against Assad began.

At least 44 people were killed then and the government blamed al Qaeda for the attack, which took place one day after the arrival of an Arab League observer mission.

On January 6, a suicide bomber killed 26 people and wounded 63 in Damascus. Syria's Interior Minister Ibrahim al-Shaar vowed an iron-fist response to the attack.

(Reporting by Dominic Evans; Editing by Angus MacSwan)