KABUL, Afghanistan - The Taliban have long exaggerated their military successes, but their recent claim that they killed more than 5,000 foreign troops in Afghanistan last year may be the militia's most startling yet.

The Taliban said last week on their website that they killed 5,220 American and NATO troops in 2008 -- an exaggerated figure nearly 20 times the official death toll.

The insurgents also said they downed 31 aircraft last year. Their

fighters destroyed 2,818 NATO and Afghan vehicles and killed 7,552 Afghan soldiers and police, according to a statement from a spokesman.

The true damage inflicted on U.S. and NATO fighters over the last year has been "repeatedly hidden by the enemy and they have controlled the media by using money, power and their lies," the statement said.

NATO and its member countries announce all troop deaths, providing names, ages and hometowns and how the soldiers were killed. According to an Associated Press tally based on those announcements, 286 foreign forces died last year in Afghanistan.

Though the death toll was highly exaggerated, the Taliban have had increased success recently. Violence in Afghanistan has spiked in the past two years, and Taliban militants now control wide swaths of countryside. In response, the U.S. is planning to pour up to 30,000 more troops into the country this year.

The insurgents' exaggerations are designed to boost morale inside the Taliban and to attract financing from donors sympathetic to their cause, a U.S. military official and a Taliban expert said.

"They put out this propaganda in order to raise capital to continue their operations," said Col. Jerry O'Hara, a U.S. military spokesman.

Vahid Mojdeh, the author of a book on the Taliban who continues to study the militia, said the exaggerated claims help the insurgents recruit new fighters.

"The Taliban needs volunteers to carry out suicide attacks, so they want to show they are killing a lot of people," Mojdeh said.

Propaganda has long been a key element in war, particularly in conflicts where the sides are fighting to win support from the population.

The Taliban exaggerate U.S. or NATO deaths in order to persuade average Afghans that the insurgents are winning, while U.S. and NATO spokesmen frequently highlight construction projects -- roads and schools -- to Afghan journalists in the hopes that average Afghans will associate foreign troops with increased development.

A Taliban spokesman, Zabiullah Mujahid, stood by the militia's numbers in a telephone interview Monday, saying that Taliban fighters film every operation and verify the tolls.

"All the time the foreign invaders are trying to hide the reality from the media," he said. "The numbers I have given to you, that is counted one by one. For example, when we are saying there are 2,818 vehicles destroyed, that is a correct number. Why aren't we saying 2,820? Because we have reports of 2,818."

Mojdeh, the Taliban expert, said that some of the exaggerations likely come from false assumptions. For instance, he said, if a roadside bomb hits a U.S. Humvee, then the Taliban probably report four U.S. deaths, even if everyone inside the armoured vehicle survived.

The Taliban updates their site every day with claims of military successes that often defy credibility. The numbers from 2008 appear to be a tabulation of those daily claims.