COLOMBO, Sri Lanka, Feb. 27 -- Rebels fired on Sri Lankan military helicopters carrying six foreign envoys Tuesday, slightly wounding the U.S. and Italian ambassadors and sending the group screaming and running for cover.

The government said it was a deliberate attack, but the rebels said they did not know that diplomats were on board.

Seven Sri Lankan security personnel also were hurt, but the envoys from Canada, France, Germany and Japan escaped without injury.

"We were extremely lucky to be able to escape. I could see the grenades or something like that falling and exploding," German Ambassador Juergen Weerth told reporters after returning to Colombo, the capital.

The delegation representing donor nations, accompanied by staff and Sri Lankan officials, was traveling to the eastern city of Batticaloa to review development in the area, a center of separatist violence that was hit hard by the 2004 Asian tsunami.

The helicopters carrying the group had just touched down at a playground used by the military as a landing ground in Batticaloa when several mortar shells exploded near the aircraft, said Mahinda Samarasinghe, a Sri Lankan government minister traveling with the delegation.

Samarasinghe's press officer, Lal Sarath Kumara, who arrived in another helicopter shortly before the attack, said everyone hit the ground when the shells started coming in and then ran for cover.

"Everyone ran in various directions. There was huge chaos there, and all the people were in fear. People were screaming and running," the press officer said.

He estimated that six shells hit the area, and added, "We escaped narrowly."

Samarasinghe said U.S. Ambassador Robert O. Blake and his Italian counterpart, Pio Mariani, "suffered slight injuries" but were fine now.

The U.S. Embassy issued a statement saying Blake was "all right" but did not elaborate. Sri Lankan doctors said the Italian ambassador was treated for a shrapnel injury to the head and was discharged less than two hours later.

Both men managed to take part in at least some of their scheduled meetings before heading back to Colombo.

"This attack has been deliberately leveled against the foreign diplomats who were undertaking a humanitarian mission," Sri Lankan Foreign Minister Rohitha Bogollagama said while visiting China.

The rebel Tamil Tigers said they were not aware the military helicopters were carrying ambassadors and blamed the army for putting the diplomats in harm's way. They said that the envoys landed in an area where the army has attacked Tamil Tigers and that their artillery attack was intended to avert further military assaults.

"I express our regret at this unfortunate incident," said Rasiah Ilanthirayan, the Tamil Tiger spokesman. "Our people were not informed of the diplomatic movement. . . . This is a criminal negligence on the part of the Sri Lankan military."

The Tamil Tigers have been fighting since 1983 for a separate homeland for the country's 3.1 million ethnic Tamils. A Norwegian-brokered 2002 cease-fire has come under serious threat as more than 3,600 fighters and civilians were killed in renewed fighting in 2006. Before the cease-fire, the conflict claimed the lives of about 65,000 people and displaced 1.6 million.

The United States and European Union consider the Tamil Tigers a terrorist group.