BAGHDAD, Iraq — Gunmen wearing military uniforms assassinated the brother of Iraq’s Sunni Arab vice president in his home yesterday — the third sibling the official has lost this year to the country’s violence.

Elsewhere, 11 Iraqi soldiers were kidnapped in a brazen attack on a checkpoint in Sadr City, a Shiite district in Baghdad.The government also said Iraqi forces had arrested a high-ranking member of Al Qaeda in Iraq.Three American Marines died Sunday of wounds suffered in fighting in Anbar region, the heartland of the Sunni insurgency, the American military said, without elaborating.

Lieutenant General Amir al-Hashimi, a Defense Ministry adviser and the brother of Vice President Tariq al-Hashimi, was killed by gunmen who entered his north Baghdad home wearing military uniforms, a ministry spokesman, Brigadier Qassim al-Moussawi, said. Insurgents have often targeted the families of prominent politicians in an apparent effort to intimidate the country’s leaders. The general’s death came five months after the vice president’s sister and another brother were killed within two weeks of each other, both in shootings in the Iraqi capital. Two militiamen were arrested shortly after the slaying of Mr. Hashimi’s sister, but the government did not say whether they were part of a Shiite or Sunni group. Tariq al-Hashimi is Iraq’s most prominent Sunni Arab political figure. In September, the vice president urged Sunni-led insurgents to quickly join Prime Minister al-Maliki’s national reconciliation effort. Mr. Maliki is a Shiite. Earlier, he had called for the insurgency to be put down by force.

Mr. Maliki condemned the killing yesterday as an “ugly, terrorist crime.”