U.S. and Iranian officials have held another round of talks in Baghdad, in what American diplomats describe as "frank and serious" discussions about Iraq's security.

U.S. and Iranian ambassadors met for their third round of talks. And for the first time, a new expert-level committee of U.S., Iranian and Iraqi officials met to discuss efforts to stabilize Iraq.

Afterward, Iranian news agencies quoted Iranian officials accusing the United States of using the negotiations for propaganda.

U.S. officials have accused Iran of supplying weapons and training to Shi'ite militias in Iraq -- a charge Tehran denies.

Also in Baghdad Monday, political divisions in the Iraqi government appeared to deepen with five Iraqi Cabinet ministers saying they will boycott government meetings. The "Iraqiya List" ministers said Prime Minister Nouri al-Maliki had not responded to political demands.

The Iraqiya List includes Sunnis, Shi'ites, and Christians loyal to former Prime Minister Ayad Allawi.

More violence was reported across Iraq, with the biggest attack killing at least 30 people and wounding some 50 others in the northern city Tal Afar.

In the town of Baquba, police reported finding 60 decomposing bodies in an area where al-Qaida in Iraq has been active. Elsewhere in Diyala province, the U.S. military reported four soldiers were killed and 12 wounded in an explosion during a combat operation.

In Baghdad, police say a roadside bomb killed at least nine people in a predominantly Shi'ite neighborhood.