A car bomb has hit a military intelligence office in the Iraqi capital, Baghdad, killing at least 13 people and injuring 25 others, Al Jazeera has learned.

The explosion on Saturday targeted the Karada neighbourhood where the intelligence office, which also houses a police station, is located.

The headquarters is protected by concrete blast walls, but the security forces on guard at its entrance on an often-crowded intersection are easy targets for attack.

The attack came a day after a Shia armed group killed at least 73 Sunni Muslim worshippers at a village mosque in Diyala province, raising the prospect of revenge attacks as politicians try to form a government capable of countering the Islamic State group.

There was no immediate claim of responsibility for the blast, but suicide bombings are a hallmark of Sunni groups, including those loyal to the Islamic State.

Al Jazeera's Jane Arraf, reporting from Erbil, said the latest bombing in Baghdad adds to the already "very volatile" security situation in the country.

An advance by Islamic State fighters through northern Iraq has alarmed the Baghdad government and its Western allies. The US has launched air strikes in Iraq for the first time since the withdrawal of its troops in 2011.

Although the air campaign has caused a few setbacks for Islamic State, they do not address the wider problem of sectarian warfare which the group has fuelled with attacks on Shias and minorities.

Bombings, kidnappings and execution-style shootings occur almost daily, echoing the dark days of 2006-2007, the peak of sectarian violence.