BAGHDAD (AP):

Iraqi security forces conducted intense searches at checkpoints in Baghdad on Monday amid warnings of more attacks, as Iraqis questioned how two buses packed with explosives penetrated what was supposed to be one of the city's safest areas, killing 155 people.

Sunday's twin suicide blasts in the heart of the capital targeting the justice ministry and the Baghdad Provincial Administration were the worst attacks in more than two years. They raised fears about Iraq's ability to protect itself as it prepares for January elections and the United States military withdrawal.

Baghdad's top security officials brought reinforcements to guard government institutions and blocked streets around the capital, acting on intelligence suggesting such buildings could be the militants' next target, Major General Qassim al-Moussawi, a spokesman for the city's operations command center told The Associated Press.

But those measures seemed insufficient to many angry Iraqis who fear more attacks and question the ability of Prime Minister Nouri al-Maliki's government to keep the country secure.

"This explosion made people furious," said Ahmed Hassan, an employee at the Ministry of Education. "People will not re-elect this government."