The pilots sent a letter to the Israeli air force commander declaring their refusal to carry out duties, which include track-and-kill operations, in the West Bank and the Gaza Strip.

"We, veteran pilots and active pilots alike... are opposed to carrying out illegal and immoral attacks, of the type carried out by Israel in the territories," one of the pilots told Israel`s Channel 2 television on Wednesday.

"We, who have been educated to love the state of Israel... refuse to take part in air force attacks in civilian population centres. We... refuse to continue harming innocent civilians," one of the pilots told Channel 2.

The television station said almost half of those who signed the petition were flying missions once or twice a week. Israeli reserve pilots can be called upon to fly in military operations.

"We are talking of 27 pilots out of thousands," air force commander Major-General Dan Halutz told Israel Radio, apparently referring to active, reserve and retired pilots.

Air force Brigadier-General Ido Nehushtan told Reuters the 27 were a "marginal, small group".

Israel`s army chief, Moshe Ya`alon, said the pilots, who include senior reserve officers in the air force, could be punished for what he called their illegitimate and forbidden statement.

"If we`ll need to take steps (against them), we`ll take them... We have to examine the matter," he told Channel 2.

Israel has killed 12 Hamas militants in air strikes in the Gaza Strip since a Hamas suicide bombing killed 23 people in Jerusalem on August 19.

Several bystanders have also been killed in the attacks, which Israel has used to assassinate top Palestinian leaders from the militant group.

Israel has an active group of conscientious objectors who have refused to serve in Palestinian territories, but the letter marks the first time that pilots protested in a separate group.

Israeli servicemen can be jailed for refusing to carry out orders.