Iran is backing a Shia insurgent campaign of systematically assassinating former elite Iraqi air force pilots as part of a covert sectarian war against Sunnis, according to senior politicians in Baghdad. The spate of murders of pilots has prompted an intervention from Jalal Talabani, Iraq's president, who has offered them safe haven in his native Kurdistan even though some of them were involved in dropping chemical weapons there. Alleged Iranian involvement in the killings has heightened sectarian tensions in Iraq and could increase diplomatic pressure on Tehran. Former senior military officers, overwhelmingly from Saddam Hussein's favoured Sunni sect, are among the most alienated groups in Iraq and form a key element of the Arab nationalist section of the insurgency.In an effort to woo these officers away from their alliance of convenience with Islamist foreign fighters, Mr Talabani, a Kurd, held a meeting with more than 1,000 in Baghdad. Afterwards, according to coalition sources, several Kurdish officials entered the room and set briefcases down on tables. The briefcases were opened to reveal wads of new $100 bills. Each officer was then given $1,000 as compensation for the loss of his pension. Mr Talabani told The Sunday Telegraph: "I openly called in a meeting I had with 1,000 Arab Sunni former high-ranking officers for them to come to Kurdistan and live in peace." He said he was unsure who was behind the murders of the pilots but suggested they were reprisals for war crimes. "I don't know whether it is revenge for bombing civilians, for bombing Iran, for bombing Kurdistan."