Baghdad, Iraq ? Capping the bloodiest month for American troops since January, the U.S. military reported Monday that seven more U.S. service members were killed – all victims of increasingly sophisticated bombs that have been become the deadliest weapon in the insurgents’ arsenal.

Bombs also claimed a toll Monday among civilians in Basra, Iraq’s second-largest city and the major metropolis of the Shiite-dominated south, which has witnessed less violence than Sunni areas. A large car bomb exploded along a bustling street packed with shops and restaurants as people were enjoying an evening out after the daily Ramadan fast. At least 20 were killed and about 40 wounded, police Lt. Col. Karim al-Zaidi said.

Military commanders have warned that Sunni insurgents will step up their attacks in the run-up to the Dec. 15 election, when Iraqis will choose their first full-term parliament since the collapse of Saddam Hussein’s regime in 2003.

To guard against such attacks, the military has raised the number of American troops in Iraq to 157,000 – among the highest levels of the Iraq conflict.

Most of the combat deaths and injuries in recent months have been a result of the increasing use by insurgents of sophisticated homemade bombs, responsible for the deaths of the seven Americans killed since Sunday. The military refers to those bombs as “improvised explosive devices,” or IEDs.

Iraqi firefighters work at the site of the blast after a car bomb exploded Monday in Basra, Iraq. At least 20 civilians were killed in the bombing, and about 40 were wounded.

Last Friday, an IED killed Col. William W. Wood, 44, of Panama City, Fla., an infantry battalion commander. He was promoted posthumously, making him the highest-ranking soldier killed in action in the Iraq conflict, according to the Pentagon.

Monday’s deadliest attack against U.S. service members came in an area known as the “triangle of death.” Four soldiers from the U.S. Army’s Task Force Baghdad died when their patrol struck a roadside bomb in Youssifiyah, 12 miles south of Baghdad.

Two other soldiers from the Army’s 29th Brigade Combat Team also were killed in a bombing Monday near Balad, 50 miles north of the capital. The U.S. military also reported that a Marine died the day before in a roadside bombing near Amiriyah, an insurgent hotspot 25 miles west of Baghdad.

The U.S. military death toll for October is now at least 92, the highest monthly total since January, when 106 American service members died – more than 30 of them in a helicopter crash that was ruled an accident. Only during two other months since the war began has the U.S. military seen a higher toll: in November 2004, when 137 Americans died, and in April 2004, when 135 died.

The latest deaths brought to 2,025 the number of U.S. service members who have died since the Iraq war began in March 2003. The number includes five military civilians.