KABUL - A motorcycle bomb struck a crowd watching a dog fight Friday in southern Afghanistan, killing at least three people and wounding more than two dozen others.

The blast on the outskirts of Lashkar Gah, capital of Helmand province, came as U.S. Marines and their NATO and Afghan allies are poised to launch a major offensive against the Taliban in the area.

The explosives-packed motorcycle was parked near the dog fight, according to deputy provincial police chief Kamal Uddin.

Health Department director Dr. Inayat Ullah Ghafari confirmed the casualty toll, saying seven children were among the 26 wounded.

Dog fighting was forbidden under the Taliban regime but has emerged as a popular pastime in many parts of Afghanistan after the hard-line Islamist movement was ousted in 2001.

Such competitions have been targeted in the past. More than 100 people were killed in a suicide bombing at a dog fight in the southern city of Kandahar.

No date has been set for the Helmand offensive to begin, but U.S. commanders have said they plan to capture the town of Marjah, 610 kilometres southwest of Kabul, this winter.

The Taliban, meanwhile, claimed responsibility for Thursday's bombing near a roadside hotel in Kandahar, which borders Helmand.

Police and hospital official said it was a suicide car bombing that killed six people and wounded 18 wounded.

The blast occurred near a major road that is frequently used by U.S. convoys and other officials and police said the bomber may have detonated his explosives prematurely.

Taliban spokesman Qari Yousef Ahmadi said in a text message that militants had detonated a roadside bomb near the hotel, killing 15 contractors and wounding seven. The Taliban frequently give higher death tolls and Ahmadi did not specify who the contractors were.

In other violence, a U.S. service member was killed by a bomb Friday in western Afghanistan, NATO said. The brief statement gave no further details.

NATO also said a helicopter contracted by coalition forces was hit by small-arms fire Friday in the eastern province of Kapisa.

One person suffered minor wounds, but the helicopter suffered no significant damage and landed safely at a military base, the international force said in a statement.