Seven American soldiers were killed in Iraq on Saturday, as US military officials conceded that the number and lethality of attacks against US forces are on the increase.

“It is very clear that the number of attacks against US forces is up,” Major General James Simmons, deputy commander for operations in Iraq, told the Washington Post. “The attacks are being directed at us and not against other people,” he said, noting that attacks on Iraqi security forces have declined.

Seven US soldiers were killed and six wounded on Saturday in six separate attacks: in Nineveh province, two soldiers died when their patrol was hit by a roadside bomb; in Diyala province, two soldiers were killed in separate roadside bomb attacks; in Baghdad, one soldier died when a roadside bomb exploded and another was killed by small arms fire. Southwest of Baghdad, a seventh soldier died when he approached a man standing outside of a mosque; the man turned out to be a suicide bomber who then blew himself up.

Meanwhile, there is an increasing trend for insurgents to carry out  more complex attacks. “We are starting to see more sophistication and training in their attacks,” said one unidentified senior military official in Baghdad. “Clearly the trend is going in the wrong direction.”

One tactic involves the ambush or bombing of patrols and then targeting troops coming to their aid. The latest such incident claimed the lives of eight US troops on Memorial Day, when a helicopter carrying two soldiers was shot down over Diyala province. As ground forces rushed to the scene, a roadside bomb exploded killing four soldiers and wounding another four (one mortally). Then, as troops tried to clear the wreckage, another bomb exploded killing one more soldier.

Without doubt, the most lethal weapons being used against US forces are the Iranian-manufactured explosively formed penetrators (EFPs), capable of tearing through armor used to protect most US military vehicles. Roadside bombs are increasingly being identified as large, buried EFPs.

The Memorial Day attacks brought the number of US fatalities up to 127 for the month of May, the third-deadliest month for American troops since the 2003 invasion. A total of 3,487 US troops have died so far in the conflict in Iraq.