U.S. helicopter shot down in Afghanistan

KABUL (Reuters) - A helicopter belonging to U.S.-led coalition troops was shot down by small-arms fire in Afghanistan on Wednesday and America's top military officer said he was increasingly concerned about the rising violence.

The U.S. military said there were no serious injuries when the UH-60 Blackhawk helicopter was brought down south of Afghanistan's capital.

Adm. Mike Mullen, chairman of the U.S. Joint Chiefs of Staff, told reporters in Washington the Taliban had become more effective.

"I am, and have been for some time now, deeply troubled by the increasing violence there," he said. "The Taliban and their supporters have, without question, grown more effective and more aggressive in recent weeks, and as the casualty figures clearly demonstrate."

In May, more U.S. and coalition troops were killed in Afghanistan than in Iraq for the first time since those wars began, according to the Pentagon. More than 70,000 foreign troops are now deployed in the country.

The austere Islamist Taliban have vowed to step up their campaign of guerrilla, suicide and roadside bomb attacks this year to undermine Afghan support for the government in Kabul and pressure foreign troops to pull out.

"It has been a tough month in Afghanistan, but it's also been a tough month for the Taliban," U.S. President George W. Bush said in Washington. "One reason why there have been more deaths is because our troops are taking the fight to a tough enemy."

Pilots landed the stricken Blackhawk helicopter safely and evacuated all personnel before it caught fire in the Kharwar district of Logar province, where Taliban militants are active.

It was the second coalition helicopter to crash in a week. The other incident, in the northeast Kunar province, is under investigation but indications are that the helicopter crashed due to mechanical failure, a U.S. military spokesman said.

Removed from power in 2001 by U.S.-led troops, the resurgent Taliban said it shot down the helicopter with anti-aircraft rockets and said that all on board were killed.

The Taliban have brought down a number of aircraft, but so far they are not thought to have obtained surface-to-air missiles that could alter the balance of the war dramatically.

Many historians believe it was the Afghan mujahideen's acquisitions of such missiles that tipped the war against the Soviet occupation in their favour in the 1980s.

International troops rely heavily on aircraft to transport troops and supplies around the rugged mountainous country.

Elsewhere, a suicide car bomber hit a convoy of NATO forces on Wednesday, wounding two Canadian soldiers, three policemen and two civilians on a road near the southern town of Spin Boldak which lies on the border with Pakistan, said border police commander Abdul Razaq.

Hours later, the governor of southwestern Nimroz survived a suicide attack but three of his bodyguards were killed.

Mullen said he expected to see the Taliban use more suicide bombers and improvised explosive devices (IEDs).

(Additional reporting by Saeed Ali Achakzai in Chaman, Pakistan, and Andrew Gray and Jeremy Pelofsky in Washington; Writing by Sayed Salahuddin; Editing by Alex Richardson and David Storey)