Afghanistan ? A suicide bomb exploded in a crowded market Thursday in an Afghan town just a few hundred yards from where the U.S. ambassador was meeting with local leaders. Ten Afghans were killed and 50 wounded in the deadliest of a recent series of attacks.

Ambassador Ronald E. Neumann was not hurt in the blast. A purported Taliban spokesman claimed responsibility and said the insurgents hoped to kill “high-ranking Americans.”

Recent violence in Afghanistan has reinforced fears voiced by Afghan officials that the Taliban and al-Qaida may have merged some of their forces and are adopting terror tactics used in Iraq. The bombing follows a foiled plot by militants in June to assassinate Neumann’s predecessor, Zalmay Khalilzad.

Thursday’s attack occurred in Tirin Kot, capital of mountainous Uruzgan province, which has seen some of the fiercest Taliban fighting in the past year.

The bomb detonated in a market where townsfolk were trading sheep, vegetables and other local goods – about 500 yards from the home of the provincial governor, where the ambassador was meeting local officials, deputy provincial governor Abdul Aziz said.

It was unclear if the attacker purposely detonated the bomb or if it blew up prematurely.