Pakistan's army is investigating whether the leader of the Taliban in the northwest Swat Valley, said to have been wounded in an airstrike, delivered a recent radio address, a spokesman said Sunday. A local resident said the voice on the recording Tuesday was definitely Maulana Fazlullah's, but that he sounded somber and sick. Fazlullah long used illegal FM radio transmissions to rally militants and sow fear among residents in the valley, a scenic former tourist haven that largely fell prey to militancy more than two years ago. The transmissions mostly stopped after the army launched its latest offensive in Swat nearly three months ago. The operation has strong backing from the U.S., which wants Pakistan to clear safe havens for militants who threaten the war effort in neighboring Afghanistan. Nearly two weeks ago, the military said it had received credible reports that Fazlullah had been wounded in an airstrike. However, Mohammad Yaseen Khan, an electronics dealer in Swat's main city of Mingora, said he heard Fazlullah speak for three or four minutes Tuesday. That was definitely him, but not with his usual firebrand, aggressive style,'' Khan said. Rather, he was sounding like a sick man.'' Fazlullah asked his supporters not to lose spirit in the face of the army offensive, Khan said. We have inflicted heavy loses to this army, and there is a need for a last push to give them final defeat,'' Khan quoted Fazlullah as saying. Khan said Fazlullah also pledged that the jihad, or holy war, would continue until the world ends. Army spokesman Maj. Gen. Athar Abbas confirmed Sunday that the military is looking into the reports but said it's possible it was an older recording being played. Abbas has said in the past that the military has improved its ability to cut off the illegal radio transmissions faster. Capturing or killing the Swat Taliban leader would be a major boost to the army operation and a severe blow to the Taliban in the Swat Valley. It would also be psychological boost for the 2 million or so residents of Swat and surrounding districts who have been displaced to other parts of the country by the fighting. Starting last week, thousands of families began returning to Swat after the government said it was safe, even though military operations continue in the region.