BAGHDAD — Five U.S. troops were killed in separate attacks in the capital this weekend, including three in a single roadside bombing, the military said today, pushing the death toll past 100 in the deadliest month so far this year.

Both attacks occurred in eastern Baghdad, a predominantly Shiite area where American and Iraqi forces have stepped up their activities as part of a security crackdown that began on Feb. 14 to quell the sectarian violence.

In violence today, a suicide car bomber apparently targeting an Interior Ministry convoy struck an Iraqi checkpoint near a busy square in the predominantly Sunni area of Harthiyah in western Baghdad, killing four people and wounding 10, police said.

The bomber detonated his payload, causing part of the road to buckle, as he emerged from an underpass and was heading toward the checkpoint being manned by Interior Ministry commandos. Those killed included two commandos and two civilians.

The violence occurred despite stringent security measures during the security crackdown now in its 11th week.

On Sunday, Iran agreed to join the U.S. and other countries at a conference on Iraq this week, raising hopes the government in Tehran would help stabilize its violent neighbor and stem the flow of guns and bombs over the border.

Senior Iranian envoy Ali Larijani flew to Baghdad on Sunday for talks with al-Maliki and other senior Iraqi officials ahead of this week's meetings in Egypt — the highest-ranking Iranian official to visit Iraq since the collapse of Saddam Hussein's regime in 2003.

The killings of the Americans came as U.S. troops have been increasingly deployed on the streets of Baghdad and housed with Iraqi troops in joint security stations away from their heavily fortified bases, raising their vulnerability to attacks.

The roadside bomb killed three Multi-National Division-Baghdad soldiers and wounded another while they were on a combat patrol Sunday in eastern Baghdad, the military said. An Iraqi interpreter also was killed in the attack.

Another Multi-National Division-Baghdad soldier on a combat patrol was killed by small arms fire in eastern Baghdad Saturday, the military said in a separate statement.

A Marine assigned to Multi National Force-West was killed Sunday while conducting combat operations in Anbar province, a Sunni insurgent stronghold west of Baghdad, the military said.