BAGHDAD, Iraq (AP)-- The brother of Iraq's Sunni Arab vice president was assassinated Monday by gunmen who broke into his home, the third of the politician's four siblings to be slain this year.

Iraqi authorities, meanwhile, arrested the head of the mess hall at a base where up to 400 mainly Shiite policemen suffered food poisoning during a Ramadan meal amid concerns it may have been the first known attempt by insurgents to carry out a mass poisoning against police.

Baghdad was torn by new violence. A car bomb ripped through a market in a Shiite district, killing at least 10 people and wounding 23 — an attack likely carried out by Sunni insurgents.

Gunmen also kidnapped 11 policemen in a brazen assault on their checkpoint in Sadr City, a Baghdad neighborhood dominated by the Mahdi Army, the country's most powerful Shiite militia.

Elsewhere in Iraq, the U.S. military announced that three Marines died Sunday after fighting in the western region of Anbar, a hotbed of Sunni insurgents, bringing to 32 the number of American service members who have died in Iraq this month.

The death of the brother of Vice President Tariq al-Hashimi — the country's most prominent Sunni Arab politician — alarmed Sunnis and fueled their demands that the government crack down on Shiite militias.

Critics of Prime Minister Nouri al-Maliki accuse the Shiite leader of hesitating on reining in the militias because many of them — like the Mahdi Army — belong to parties in his government.

"The clock is starting to strike after today's events," Khalaf al-Alayan, a Sunni parliament member told The Associated Press. Al-Maliki condemned Monday's killing as an "ugly, terrorist crime."

Al-Hashimi's brother, Lt. Gen. Amir al-Hashimi, a Defense Ministry adviser, was slain when gunmen wearing military uniforms broke into his north Baghdad home, al-Moussawi said.

The gunmen also abducted six of the general's guards and a neighbor — who is also an official in Tariq al-Hashimi's Iraqi Islamic Party, according to party officials.

The vice president already has lost two other siblings in violence: His sister and another brother were killed within two weeks of each other in April, both in shootings in the Iraqi capital.

Two militiamen were arrested in the slaying of al-Hashimi's sister, but the government did not say to which militia they belonged. Al-Hashimi has one other brother, who is believed to be living abroad.