Two suicide bombers killed at least 15 people in Baghdad Thursday, while other insurgents launched attacks against US troops and Iraqi police across the country. Iraqi officials say more than 30 people were wounded in the massive explosions outside an Interior Ministry offices. Abu Musab al-Zarqawi's al-Qaida in Iraq group claimed responsibility for the Baghdad suicide attacks in an Internet posting. The blasts were the latest in several days of stepped-up insurgent and terrorist activity. South of Baghdad Thursday, a suicide bomber killed four policemen in a marketplace in Mahawil. To the north, gunmen killed four more policemen in Kirkuk. And in Tikrit, a suicide bomber blew up his car outside a military base, wounding a US soldier and two Iraqi troops.