BAGHDAD — Four more U.S. soldiers were killed in roadside bombings in the Baghdad area, including three in a single strike, the military said today, raising to at least 19 the number of troop deaths in the first week of August.

The U.S. military said three Task Force Marne soldiers were killed Saturday when a roadside bomb struck their convoy south of Baghdad, the military said.

One Multi-National Division — Baghdad soldier was killed and another wounded Monday when their vehicle was targeted by an armor-piercing explosively formed penetrator, or EFP, in a western section of the capital, according to a separate statement.

The numbers signaled a resurgence in attacks after July saw the lowest number of U.S. casualties in eight months. U.S. commanders have warned they expected militants to try to upstage a September report on military and economic progress in Iraq.

More than 100 American forces died each month in the April-to-June period as the incoming U.S. troops were deployed with the Iraqi army in Baghdad's dangerous streets and security outposts.

Iraq's political crisis also worsened as five more ministers announced a boycott of Cabinet meetings — leaving Prime Minister Nouri al-Maliki's unity government with no members affiliated with Sunni political factions.

Al-Maliki, meanwhile, arrived in Turkey for a state visit likely to be dominated by Turkish warnings to either crack down on rebel bases in northern Iraq or face a possible incursion. He was slated to travel to Iran on Wednesday.

Washington has accused Iran of supplying Shiite extremists with EFPs to step up attacks against American forces. Tehran denies the allegations.