JALALABAD, Afghanistan — Militants injured two security forces personnel in a grenade attack Monday on a major NATO airbase at an airport in the eastern Afghan city of Jalalabad, the local police chief said.

"A few men threw hand grenades at the airport gate and the troops returned fire and the attackers fled," said Sardar Sultani, the police chief for Nangarhar province, of which Jalalabad is the capital.

Two members of the security forces were "slightly injured", he said, without specifying if they were foreign or Afghan military or police.

Witnesses had reported seeing explosions, including rocket fire, at the entrance to the airport.

"There were no gunshots from their side or suicide attacks ... The explosions were from the grenades," Sultani told AFP. He said police were hunting the attackers, who may still be in the area.

An AFP correspondent in Jalalabad said he had heard gunfire, which lasted between 10 and 15 minutes, coming from the airport. He said that the shooting had stopped, but several helicopters were flying over the area.

NATO's International Security Assistance Force (ISAF) said it was unable to comment on the attack.

Jalalabad airport, which is heavily protected by US forces, is a key ISAF airbase.

In November 2010, eight Taliban insurgents, including one wearing a suicide belt, opened fire at the airport without inflicting casualties, before being killed.

And in June last year the Taliban attacked the same base in broad daylight with rocket launchers and a car bomb. Two foreign soldiers were injured and several militants killed.