KABUL, Afghanistan — A suicide bomber targeting an Afghan governor killed four people Wednesday, while a U.S.-led coalition helicopter crew escaped without serious injury after being shot down south of the capital, officials said.

The governor of Nimroz province, Ghulam Dastagir Azad, said a suicide bomber on foot blew himself up near the governor's convoy late in the afternoon Wednesday, killing three police officers and a civilian. Azad said he was not wounded.

Also Wednesday, gunfire brought down the UH-60 Black Hawk in the Kherwar district of Logar province. The pilots landed the aircraft and evacuated before it caught fire, a coalition statement said.

Another helicopter returned later and destroyed the wreckage with precision fire, it said.

Logar police Chief Mohammed Mustafa Khan said reports from his officers in the remote district suggested Taliban militants shot down the helicopter with a rocket-propelled grenade.

NATO said the suicide car bomber tried to hit a patrol near the town of Spin Boldak near the Pakistan border. Initial reports showed no troops were hurt, but there were "some local national" casualties, it said.

Gen. Abdul Raziq, a border police commander in Spin Boldak, said two construction workers and two security guards were wounded.

Helicopter crashes have been among the deadliest incidents for international troops in Afghanistan.

Most recently, seven soldiers died when a Chinook helicopter was shot down during an air assault in the southern province of Helmand in May 2007.

However, mechanical failure and accidents are as great a risk as enemy fire in Afghanistan's craggy mountains and dust-filled deserts.

Wednesday's incident comes amid a surge in fighting between insurgents and security forces across the southern half of Afghanistan, including in provinces adjacent to the capital, Kabul.

Last week, three U.S. soldiers and their Afghan interpreter were killed in a roadside bomb attack 40 miles (70 kilometers) south of the city.

Their deaths helped make June the deadliest month for foreign troops in Afghanistan since the Taliban's ouster in 2001.

Associated Press reporter Noor Khan in Kandahar contributed to this report.