Yemen's air force has been the target of "sabotage", the country's military aviation chief said in a televised interview, days after a fighter jet crashed in the capital Sanaa.
"The air force is the target of systematic sabotage," General Rashed al-Janad told the private channel Al-Saida in the interview broadcast late on Friday.
He said the Sukhoi SU-22 that crashed in Sanaa last Monday, killing the pilot, was caused by "shots hitting the aircraft" as it prepared to land at a base next to the capital's airport.
"The black box of the aircraft was hit" in the attack, he said without giving further details. He quoted witnesses as saying the jet had exploded 50 metres (yards) above the ground.
The air force said it would open an investigation into the crash, the second time a Sukhoi jet has crashed over the capital since the start of the year.
On February 19, a Yemeni air force jet crashed into a residential area of Sanaa, killing 12 people, including the pilot.
Janad said an Antonov M26 that came down north of Sanaa in November 2012 "had also been hit by shots that caused a fire in one of its engines".
He added that two other military aircraft, including a helicopter, had been fired on last November near Sanaa, although they had not been hit.
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On Wednesday, an army helicopter carrying Transport Minister Ahmad bin Dagher had to make an emergency landing in the central Bayda province after it was shot at three times, Janad said in the interview, adding that security forces had arrested 12 men over the attack.
But Janad said these acts of "sabotage" took on a new dimension with the explosion on May 6 of two refuelling vehicles at Al-Anad air base in southern Yemen, the largest in the country.
"The aim was to blow up the base's fuel store, but the fire was quickly brought under control," he said.
Janad replaced a half-brother of ousted president Ali Abdallah Saleh as Yemen's air force chief a year ago, as part of a restructuring of the armed forces.
The general said those who had been affected by the restructuring may be behind the acts of sabotage targeting the air force.
Meanwhile, President Abdrabuh Mansur Hadi urged vigilance from the air force.
"We are fighting forces who do not want the best for Yemen, or security and stability in the country," he said in a visit to the air force's headquarters on Saturday.
Without giving further details, Hadi said these forces were "working to shake the unity of the army, but they will not succeed in their aims and they will be eradicated," official news agency Saba quoted him as saying.
Supporters of Saleh, who have been accused of hampering Yemen's political transition, were removed from top military and security posts after he left power in February 2012 following a year of widespread protests.