The Nigerian Air Force (NAF) said in a statement its fighters on Monday encountered "an ambush set up by armed bandits at Kawan Pole Waya" in Kaduna state, along the notorious Kaduna-Birnin Gwari road.

The troops were able to fight their way out of the ambush, but "unfortunately, two NAF personnel paid the supreme price in the process".

Kidnapping for ransom is common in Nigeria. The victims are usually released after a ransom is paid although police rarely confirm if money changed hands.

Scores of people have been kidnapped or killed along Kaduna-Birnin Gwari road in recent months, prompting the government to deploy troops there.

Villages in the nearby Birnin Gwari region have been deserted for fear of raids by criminal gangs.

Five Chinese citizens kidnapped in April were freed a month later in a forest in Birnin Gwari.