Witnesses say supporters and opponents of Iraqi Prime Minister Nouri al-Maliki's reform actions clashed in Baghdad on Friday.

Iraqis massed in cities across the country to mark the expiration of the prime minister's 100-day deadline for improved government performance.

Opponents voiced their displeasure at what they say is a lack of progress. Loyalists rallied in support of the government measures with news reports saying some called for the execution of insurgents who have been rocking the country with attacks.

In Baghdad, there are reports of tribal loyalists attacking young anti-government demonstrators.

In a separate development, a Shi'ite militant group has claimed responsibility for a deadly attack that killed five U.S. soldiers this week.

Kataib Hezbollah posted a statement on an its website late Thursday saying it carried out the Monday rocket attack on a U.S. installation in Baghdad.