Coalition officials say four U.S. soldiers were killed by a roadside bomb in eastern Afghanistan Monday.
No further details were immediately available.
Separately, Britain's Defense Ministry said a British soldier was killed in an explosion in southern Helmand province Sunday.
In recent weeks, 4,000 U.S. Marines, along with British and Afghan troops, have launched a major offensive in southern Afghanistan, targeting Taliban insurgents in their traditional strongholds.
Meanwhile, NATO officials say a British fighter jet has crashed at the coalition's largest base in southern Afghanistan, injuring the two pilots.
NATO officials say the crash occurred early Monday at Kandahar air base. Officials say the two pilots ejected from the aircraft and were taken to the base's hospital for treatment. No one else was hurt.
The incident comes one day after a civilian helicopter crashed at the same base, killing 16 people. There is no indication that insurgent activity caused either crash.
It also is the fourth aircraft to go down in last few days.
In other news, U.S. Secretary of State Hillary Clinton says the United States is doing everything it can to find and free an American soldier captured by the Taliban in Afghanistan.
U.S. Defense Secretary Robert Gates said at a briefing Monday that he was "disgusted" at the Taliban's release of a video showing captured Private Bowe Bergdahl. U.S. military officials have said the use of the 23-year-old soldier for propaganda purposes is against international law.
Clinton also called the video "outrageous" and said it was, in her words, a "real sign of desperation" on the part of the militants.
Taliban insurgents posted the 28-minute video on a Web site Saturday. Bergdahl went missing from his base on June 30th.