KABUL, Afghanistan - U.S. and NATO deaths from roadside and suicide bomb blasts in Afghanistan soared sixfold in July compared with the same month last year, as militants detonated the highest number of bombs of the eight-year war, figures released yesterday showed.

Three U.S. Marines and a Polish soldier were killed in the latest attacks, setting August on course to surpass the record 75 deaths of U.S. and NATO troops from all causes in July.

U.S. commanders have long predicted that 2009 would be the deadliest of the war, after President Obama ordered an additional 21,000 troops here to try to quell the rising Taliban insurgency. A record 62,000 U.S. troops are in Afghanistan.

U.S., NATO, and Afghan troops are working to protect voting sites so Afghans can take part in their second-ever direct presidential election Aug. 20. Taliban militants have vowed to disrupt the elections, and attacks are rising around Afghanistan, where roadside bombs are now the cause of the majority of U.S. and NATO deaths.

Last month, 49 coalition troops were killed in bomb attacks, a more than sixfold increase from the eight killed in roadside and suicide bombings in July 2008, according to figures from the U.S.-based Joint IED Defeat Organization.

The number of incidents from IEDs, or improvised explosive devices, soared to 828, the highest level of the war and more than twice as many as in July 2008.

Of the 828 incidents, 410 bombs were found and neutralized, and 310 were ineffective. But 108 bombs were effective, triple the 36 effective attacks a year ago; the increase suggests that militants are getting better at placing and detonating bombs.

"The major challenge today for us is roadside bombs and suicide attacks," said Gen. Mohammad Zahir Azimi, spokesman for the Afghan Defense Ministry.

Azimi said Taliban fighters had figured out that roadside bombs were efficient and effective. "They stay safe," he said, "while the other side suffers."

Although roadside bombs target troops, they have killed a record number of civilians this year as well. Nine Afghans riding in a vehicle died in a bomb blast yesterday in Kandahar province, said Daud Farhad, a doctor at Kandahar's Mirwais hospital.

Afghan soldier deaths from IEDs are also up sharply, Azimi said, but he had no figures. A roadside bomb in Zabul killed two Afghan soldiers yesterday, Lt. Gen. Sher Mohammad Zazai said.

At least 14 NATO troops, including at least seven Americans, have been killed this month in bomb blasts.

Even as bomb blasts spike in Afghanistan, such attacks have dropped precipitously in Iraq.

No coalition troops died in Iraq last month from bomb attacks, only the second month that has happened since the military began keeping statistics in June 2003.

The number of IED incidents in Iraq fell from 557 in July 2008 to 166 last month.