BAGHDAD -- A suicide bomber plowed into an Interior Ministry building in central Baghdad on Tuesday, killing 21 people and wounding more than 80 in an attack that raised fears that extremists were escalating a campaign of bombings aimed at destabilizing the government.

The attack came a day after a triple bombing against three major Baghdad hotels, in which 37 people died. Though there have been several occasions in recent months in which multiple bombings have taken place, it has become rare in the Iraqi capital for suicide attackers to strike twice in as many days.

Tuesday's attack targeted a building housing a forensics-crime laboratory, and it fit a pattern of recent bombings against government institutions and high-profile landmarks ahead of the pivotal national elections due to be held in March. The bomb pulverized blast walls intended to protect the facility, caused extensive damage to the building and shattered windows for hundreds of yards around.

People at the scene accused the Iraqi security forces of failing to protect them. But they mostly blamed the former Baath Party, which ruled Iraq under Saddam Hussein, reflecting the official government view that Baathists were responsible for most of the bombings.

"The Baathists are ready to ally with even the devil, not only al-Qaida, to create unrest," said Marwan Abid Salman, 35, who lived near the bomb site.

The top U.S. military commander in Iraq, Gen. Ray Odierno, said he was convinced that al-Qaida in Iraq was behind the latest attacks, perhaps acting in coordination with some Baathists. "We don't have proof yet, but I believe this was al-Qaida," he told journalists.

Gen. Odierno noted that Monday's bombings featured a new tactic, in which gunmen helped the bombers gain access to two of the hotels by firing on guards at the gate.

The bombings showed that al-Qaida still was capable of launching sophisticated attacks, but Gen. Odierno said he believed that it lacked the capacity to mount a sustained campaign. "They are doing a lot less attacks," he said, "but they are trying to get a bigger outcome."

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