SRINAGAR, India, August 1 (AP)--A group of pilgrims on their way to a Hindu religious shrine came under fire Tuesday in an attack that left at least 21 dead and 30 injured, a top official said.

No one immediately claimed responsibility for the attack at Pahalgam, about 55 miles ( 88 kilometers) south of Srinagar, the capital of Kashmir. But police said they suspected Islamic guerrillas fighting for Kashmir's independence.

Security forces and police fired back at the gunmen who fled, said police and army officials reached by telephone. Two militants and a policeman were among those killed, Kulbushan Jandiyal, director of information of the state government, told The Associated Press.

Twelve pilgrims were among those injured, he said. The others included local businessmen, porters and men hiring out horses to carry pilgrims up the steep slopes.

Thirteen people were admitted to the S.M.H.S. Hospital in Srinagar, the state capital, where the condition of three of them was serious, doctors said.

"We were standing by the river. Suddenly we heard gunshots. We couldn't see from where it was coming. I fell down.... I realized I had been hit," said Nandu Agarwal, who was hospitalized.

Muzaffar Wani, a Muslim businessman who sells trinkets, said he heard a first round of gunshots, then a second round from security forces.

"It was chaotic. We couldn't see who was firing at us," he said, lying on a hospital bed.

It was the first time that the guerrillas have opened fire and killed pilgrims on their way to the Amarnath Cave, a religious site for Hindus in the mountains that takes two days to trek to.

The cave contains an icy stalagmite resembling Shiva, the god of death who is worshipped for destroying a person's ego.

Police immediately put Amarnath under curfew to prevent violence and to hunt for the militants.

The government provides extensive security for the pilgrims in light of threats to them from the separatists, who have been fighting security forces for 11 years.

Army soldiers and paramilitary soldiers fanned out across the mountains to search for the assailants.

Some 20,000 pilgrims are camping in tents and hotels in Pahalgam, where they begin a 30-mile (48-kilometer) trek into the mountains.

Two-thirds of Kashmir is controlled by India and the rest by Pakistan. More than a dozen guerrilla groups have been fighting security forces to make Kashmir independent.