BAGHDAD -- A double bombing tore through Kurdish political party offices in northern Iraq in the deadliest of a series of attacks nationwide that killed at least 40 people, officials said. It was the second such assault in as many days.

Nobody claimed responsibility for Monday's attack. But an al-Qaida splinter group known as the Islamic State of Iraq and the Levant claimed responsibility for the previous double bombing Sunday against Kurdish offices in Jalula, northwest of Baghdad, killing 19 people. The group said in an online statement that the bombings in Jalula were in response to the detention of Muslim women by authorities in the self-rule Kurdish region in northern Iraq.

Iraq is grappling with its worst surge in violence since the sectarian bloodletting of 2006 and 2007, when the country was pushed to the brink of civil war despite the presence of tens of thousands of U.S. troops. The Americans withdrew at the end of 2011.

Monday's attack took place in the town of Tuz Khormato, about 200 kilometers (130 miles) north of Baghdad, when a suicide bomber drove his explosives-laden truck into a checkpoint leading up to the offices of the Patriotic Union of Kurdistan and the nearby Kurdistan Communist Party.

Mayor Shalal Abdoul said another truck bomb exploded, presumably detonated by remote control, as people rushed to the scene of the first attack. The blasts killed 22 people, wounded as many as 150 and destroyed several houses and cars, he said.

The Patriotic Union of Kurdistan of Iraqi President Jalal Talabani is one of the main parties governing the Kurdish region in northern Iraq and maintains offices in other areas that are heavily dominated by the ethnic minority.

The Islamic State of Iraq and the Levant is composed of Sunni insurgents who stage frequent high-profile bombings aimed at derailing the Shiite-dominated government and its Kurdish allies.

Attacks have spiked as Islamic State and other insurgents have strengthened their control over parts of Iraq's western Anbar province and exploited widespread Sunni anger over alleged mistreatment by the government.

Also Monday, gunmen opened fire on a security checkpoint in the town of Kanaan, about 75 kilometers (50 miles) northeast of Baghdad, killing four soldiers and two police officers, police said.

And in the Iraqi capital, gunmen killed a real estate agent after spraying his office with bullets in a western neighborhood, police said. A bomb blast also killed a government employee in eastern Baghdad, police said.

Police also said a bomb on a boat destroyed a Euphrates River bridge linking a road between the Anbar city of Fallujah and southeastern Baghdad. No casualties were reported.

Shortly before sunset, a suicide bomber drove his explosive-laden tanker truck into the gate of a military unit in the northern city of Mosul, killing three soldiers and wounding 15, police said.

At night, a car bomb explosion in a square in Baghdad's eastern Shiite district of Sadr City, killing four people and wounding nine others. Minutes later, two separate bomb attacks in two districts in Baghdad killed three people and wounded seven, according to officials.

Medical officials confirmed the casualties for all attacks. All officials spoke on condition of anonymity because they were not authorized to speak to journalists.

Meanwhile, the head of Anbar's provincial council, Sabah al-Karhout, said 15 Anbar University staff members were still missing after a brazen attack by gunmen who stormed a campus building on Saturday.

The situation has largely been brought under control, but Karhout told reporters Monday that university authorities have said about 15 staffers are still missing, likely held by a group of gunmen in a campus building. More than $10 million was looted from the university safe, he said. (AP)