The Taleban leader urged his followers not to fear death
The reclusive one-eyed leader urged fighters to show patience as they waged holy war.
Mullah Omar is believed to have fled the southern stronghold of Kandahar, where AIP said four people were killed in the latest US military strike.
Mullah Omar's message came as US air strikes reportedly targeted Taleban front-line positions close to Kabul for the first time. The Islamic militia is also battling to defend the key northern city of Mazar-e-Sharif from advancing opposition forces.
Alive and well
"You have to apply endurance and stamina," AIP quoted Mullah Omar as saying.
"I am convinced that God will defeat the big infidel and cause its downfall," he said on the 11th day of the US-led bombardment of Afghanistan.
AIP said the broadcast showed that Mullah Omar was apparently still alive and unharmed by the military onslaught.
But the Taleban's spiritual leader, who is rarely seen and has only been photographed once, said his forces should not fear death.
"Death will definitely come one day; we don't care about this," he said, comparing the conflict to the jihad waged against Soviet forces during the 1980s.
"We just want to perish as Muslims...the goal is martyrdom," he said.
Further deaths
AIP reported that four people were killed in a US raid on the southern Taleban stronghold of Kandahar on Wednesday.
The report said Kabul airport was also hit.
Mullah Omar's residential compound and offices in Kandahar were reportedly among the first targets of the bombing campaign.
Mullah Omar's whereabouts are unknown, as is the hiding place of Osama Bin Laden, the man blamed by the US for a range of attacks on its citizens.
Front-line bombed
A Northern Alliance spokesman said their troops were receiving air support near the Afghan capital from the Americans, but there was no confirmation from the Pentagon.
Northern Alliance fighters have also renewed their efforts to capture the strategic town of Mazar-e-Sharif in northern Afghanistan, an official said.
The Associated Press news agency quoted an opposition spokesman as saying alliance forces had moved as close as seven kilometres (four miles) to the city's airport.
BBC Monitoring, based in Caversham in southern England, selects and translates information from radio, television, press, news agencies and the internet from 150 countries in more than 70 languages.