(Adds background and details on bomber)

BAGHDAD, Jan 2 (Reuters) - A suicide bomber struck a lunch gathering of Sunni Arab tribal leaders on Friday in a town south of Baghdad, killing at least 23 people and wounding 42 others, security spokesman Major-General Qassim Moussawi said.

The U.S. military said its initial reports said 21 were killed and 44 were wounded. An Iraqi security source said as many as 30 people died and more than 100 were hurt.

Moussawi said Sheikh Mohammed Abdullah Salih, a leader of the Sunni al-Qaraghouli tribe, hosted the lunch for tribal leaders at his home.

The bomber, a relative of the host named Amin al-Qaraghouli, entered through the rear gate of the house and blew himself among the guests, Moussawi said. The sheikh was among the wounded.

Violence has dropped sharply in Iraq from the peak of sectarian bloodshed in 2006 and 2007, but suicide bombs and other attacks still shake its fragile peace regularly.

A suicide bomber killed around 50 people at a packed restaurant near the northern city of Kirkuk on Dec. 11.

Friday's bombing took place a day after the United States presence in Iraq officially came under Iraqi government authority according to a security pact that took effect on New Year's Day.

The 140,000 U.S. troops in Iraq are gradually reducing their activities ahead of an end-2011 departure deadline.

AlertNet news is provided by