Getting your Trinity Audio player ready...

A day after U.S. forces killed at least 18 Taliban fighters in clashes near here, more than 300 American soldiers scoured a sprawling complex of 160 caves and hide-outs Wednesday in southeastern Afghanistan, U.S. military officials said.

No more fighters were encountered, but military officials said the cave complex suggested that Taliban soldiers had been mounting a large-scale, covert effort to establish a major base inside Afghanistan, in the Adi Ghar range 20 miles north of the small American military post in Spin Boldak.

American soldiers found evidence that wounded fighters had been kept in the caves, military officials said. They also found mules and stockpiles of ammunition, fuel, food, water and blankets.

Afghan officials said a cross-border resupply system involving shopkeepers, trucks and motorbikes allowed Taliban fighters to smuggle weapons from nearby Pakistan into the caves, built by Afghan guerrillas fighting the Soviets in the 1980s. Together with incidents over the last several weeks, the complex and evidence within suggest that Taliban commanders are using bases in Pakistan to reorganize and reassert themselves.

“There is only one route,” said Ubaidullah Mama, an Afghan commander whose troops are fighting alongside Americans forces.

Afghan officials have expressed alarm that the recent electoral success of hard-line Islamic political parties in Pakistan will allow fighters for the Taliban and Al Qaeda to use border areas in Pakistan as havens. In October elections, the religious parties won control of two border provinces as well as a record 20 percent of seats in the national parliament.

Dozens, possibly hundreds, of Taliban and Al Qaeda fighters are believed to be hiding just over the border in Pakistani tribal areas with the support of local militants. Pakistani officials say they are trying to stamp out militancy. Critics contend the effort is halfhearted and that Pakistan’s military and intelligence services are still closely tied to militants.

The complex discovered on Monday is the first tangible evidence of the breadth of the Taliban reorganization effort. Local Afghan officials believe the rebels’ leader is Hafiz Raheem, a former mujahedeen chief who belongs to the Islamic Party, or Hezb-e-Islami, of Gulbuddin Hekmatyar, a regional warlord. Hekmatyar, an Islamic militant whom the United States heavily financed during the war against the Soviets, has now declared war on American forces in Afghanistan.

Raheem, who is from Spin Boldak, later joined the Taliban. Gen. Muhammad Akram Khakrezwal, police chief of the regional capital, Kandahar, said Raheem is trying to regain a local footing and to stage attacks against the U.S. presence there.

“He wrote his name on leaflets that were distributed there,” Khakrezwal said. “He wants a return of the Taliban and Hezb-e-Islami.”