Three Americans were among five foreign troops killed in Afghanistan on Sunday, continuing a deadly trend ahead of a presidential election this month, Reuters reported.
The deaths were the latest in an escalation of violence which threatens to overshadow the Aug. 20 ballot, a poll seen as a test for both Washington and Kabul after eight years of war.
The Taliban have vowed to disrupt the election and have called on Afghans to boycott the ballot, the second direct vote for president since the Islamists were toppled in 2001.
A statement by NATO-led foreign forces said a patrol was hit by a roadside bomb in the east on Sunday and was then attacked with small-arms fire. The three troops were killed during the engagement with unidentified insurgents, NATO said.
U.S. military spokeswoman Lieutenant Commander Christine Sidenstricker identified the three as American. No other details were immediately available.
The International Security Assistance Force in Afghanistan also said on Sunday that two soldiers were killed when their patrol was hit by two roadside bombs in the volatile south.
Sidenstricker said the two were not American.
August has so far followed the bloody trend of July, with nine foreign troops killed in the first two days. Three more Americans and a French soldier were killed on Saturday.
At least 71 foreign troops were killed in July. This included 41 U.S. troops, well above the previous monthly high of 26 in September 2008, and 22 British soldiers.
And the United Nations said on Friday 1,013 civilians had been killed between January and June this year, up from 818 in the same period last year. The Taliban and other insurgents were responsible for 59 percent of civilian deaths, a U.N. human rights report said.
Attacks this year had already reached their worst level since the removal of the Taliban and escalated after U.S. Marines and British troops launched offensives in southern Helmand province last month.
Military commanders had said a spike in casualties could be expected during the operations.
Helmand, a sprawling province of deserts, lush river valleys and mountains, has long been a Taliban stronghold and the source of most of the opium that funds the insurgency.
The offensives are the first operations under U.S. President Barack Obama's new regional strategy to defeat the Taliban and its militant Islamist allies and stabilise Afghanistan.
There have been a series of election-related attacks across the country, with one of President Hamid Karzai's campaign convoys ambushed in southeastern Ghazni on Saturday. A bodyguard was killed and a candidate for provincial elections was wounded.
The election is seen as a test of Obama's new strategy, as well as Kabul's ability to stage a legitimate and credible poll.
Karzai is seen as a clear front-runner in a field of 36 contenders. Poor security appears as one of the few election threats to the man who has ruled since 2001 and won the country's first direct vote in 2004.
A low voter turn-out in the ethnic Pashtun south, Karzai's traditional power base, could raise the possibility of a second run-off vote if no candidate gets more than 50 percent in the first round.
This would then open the way for a consolidation of rivals behind one of Karzai's main challengers, former foreign minister Abdullah Abdullah or former finance minister Ashraf Ghani.