BAGHDAD ? �An al-Qaida affiliated group in Iraq has claimed responsibly for a double bombing that targeted a counterterrorism unit in Baghdad last month.

The al-Qaida statement claimed 70 people were killed in the July 31 attack on the security headquarters. Government and security officials put the death toll for all the violence that hit the capital that day at 21.

In a statement posted Monday on a militant website, the Islamic State of Iraq, al-Qaida's Iraqi branch, said a group of "believers from the Sunni people" attacked a unit that is part of the pro-Iranian forces in the country. Iran is a regional Shiite powerhouse.

Security forces and government offices are top targets for insurgents seeking to undermine the Shiite-led Iraqi government's authority.