~ A missile brought down one aircraft; officials ruled out hostile fire for the second.

Ten U.S. soldiers died when their helicopter crashed during combat operations in eastern Afghanistan, while a British military helicopter apparently was hit by a missile and crashed in Basra, Iraq, killing four crew members, officials said Saturday.

The crash of the CH-47 Chinook Friday afternoon was the deadliest for U.S. forces in Afghanistan in a year and comes at a time of increasing militant attacks, though U.S. officials ruled out hostile fire as a cause.

"There is no indication that the helicopter came down due to some enemy action," said Lt. Tamara D. Lawrence, a coalition spokeswoman.

Some 2,500 Afghan and U.S. soldiers are conducting a joint military campaign, dubbed Operation Mountain Lion, in Kunar province near the border with Pakistan. It is one of the biggest offensives since the ouster of the hard-line Taliban regime by U.S.-led forces in late 2001 for hosting al-Qaida.

The transport helicopter was conducting "operations on a mountaintop landing zone" when it crashed near Asadabad in Kunar, about 150 miles east of the capital, Kabul, the military said.

The terrain surrounding Asadabad -- where the U.S. military has a large base -- is extremely rugged. The police chief of Kunar province, Gen. Abdul Ghafar, said the helicopter crashed about 10 miles northwest of the base at a remote spot a day's walk from any passable road.

Recovery operations did not begin until daybreak Saturday. The military did not say what unit the U.S. troops were from, only specifying that they were soldiers.

The crash of the British helicopter in Basra triggered a confrontation in which jubilant Iraqis pelted British troops with stones, hurled firebombs and shouted slogans in support of a radical Shiite Muslim cleric.

Iraqi police said four British crew members died in the crash in the southern city, and four Iraqi adults and a child were reported killed during the ensuing melee when Shiite gunmen exchanged fire with British soldiers who hurried to the scene. About 30 civilians were injured.

Reminiscent of other outbursts of Iraqis cheering the deaths of foreigners, the chaotic scene was widely shown on Iraqi state television and on the Al-Jazeera satellite station.

The violence underscored that discontent over the presence of foreign soldiers has been growing among Iraq's majority Shiites even though they have generally steered clear of the Sunni Arab-dominated insurgency.

Police Capt. Mushtaq Khazim said the helicopter went down in a vacant lot between two houses after it was struck by a shoulder-fired missile -- a weapon widely available among insurgent groups and armed militias in Iraq. He said the four crew members were killed.

British soldiers with armored vehicles rushed to the site and were met by a hail of stones from a crowd of at least 250 people, many of them teenagers, who jumped for joy and raised their fists as thick smoke rose from the wreckage.

As many as three armored vehicles were set on fire, apparently with gasoline bombs and a rocket-propelled grenade, but the troops inside escaped unhurt, witnesses said.

The crowd chanted "we are all soldiers of al-Sayed," a reference to radical Shiite cleric Muqtada al-Sadr, an ardent foe of foreign troops being in Iraq.

Calm returned by nightfall as Iraqi authorities imposed a curfew and hundreds of Iraqi police and soldiers set up checkpoints and patrolled the streets, residents said. Sporadic rocket fire could be heard throughout Basra, Iraq's second largest city.