Twin suicide bomb attacks in the northern Iraqi city of Irbil have killed at least 56 people and injured more than 200 others. Officials say the casualty figures are expected to rise.

Two suicide bombers managed to get past security checks and make their way into crowded meeting halls in Irbil. One bomber blew himself up at the headquarters of the Kurdistan Democratic Party, the other at the offices of the Patriotic Union of Kurdistan.

Both sites were full of people who had come to celebrate the Muslim holiday of Eid al-Adha. Some senior Kurdish officials are reported among the casualties.

Morgues and hospitals were overflowing as medical personnel tried to cope with the influx of casualties. Authorities declared a state of emergency in the area and appealed for calm.

No one has yet claimed responsibility for the attack. Some Kurdish officials point the finger at an extremist Islamic group, Ansar al-Islam. The group is believed linked to the al-Qaida terrorist network.

Authorities had warned of increased violence ahead of and during the Eid al-Adha holiday.

On Saturday, at least nine Iraqi civilians and police officers were killed when a car carrying explosives blew up in front of a police station in the northern city of Mosul. Forty-five other people were wounded by the blast.

In a separate attack, U.S. officials say three American soldiers were killed when their convoy was struck by a roadside bomb blast between the towns of Tikrit and Kirkuk. Later Saturday, witnesses say at least five people were killed in explosions in a crowded Baghdad neighborhood.

Meanwhile, Deputy Defense Secretary Paul Wolfowitz is visiting Iraq to get a first-hand look at the situation and see how the rotation of American forces in and out of the country is progressing.