ISLAMABAD (AP) - Taliban gunmen stopped an army convoy from entering their valley stronghold, casting a U.S.-criticized peace deal back into doubt a day after the militants called off a move closer to the Pakistani capital.

Meanwhile, nine children were killed in the northwest Lower Dir region, when an old shell they were playing with exploded.

About 50 militants blocked the main road leading into the northwestern valley of Swat on Saturday, halting a column of six army trucks and two jeeps, Taliban spokesman Muslim Khan said.

The vehicles were carrying extra troops as well as supplies, in violation of the peace accord, Khan told The Associated Press by telephone.

A military official confirmed the incident and said the convoy returned to the nearby town of Bari Kot. He declined to give details and spoke on condition of anonymity because he was not authorized to discuss it publicly.

Pakistani authorities agreed in February to impose Islamic law in Swat in return for a cease-fire after nearly two years of bloody fighting in the former tourist haven.