BBC News Online: World: South Asia

Hi-tech and hearsay in Bin Laden hunt

Infra-red sensors can be used by both aircraft and soldiers

Radio broadcasts and leaflets dropped from US planes are telling the Afghans about America's offer of a $25m cash reward for the capture of Osama Bin Laden.

"We are getting scraps of information from people on the ground saying that they understand this has happened or that has happened," said US Defence Secretary Donald Rumsfeld.

"Where we get information that leads us to believe that al-Qaeda or Taleban leaders are gathered, we have been targeting those facilities."

Defence experts say the US is desperate to avoid having to send in more US troops to comb the country's vast complex of caves in the hope of flushing out Bin Laden, whom it blames for the terrorist assaults of 11 September.

Hot and cold

Sensors capable of detecting heat, magnetic fields and vibrations are being deployed which can be used both by aircraft or by troops on the ground.

"You can't see into caves but these sensors are capable of picking up movement on the ground, as well as the use of electronic equipment and generators," defence analyst Andrew Brookes from the International Institute of Strategic Studies told BBC News Online.

As the freezing Afghan winter sets in, any warmth being generated on the ground will be easier for these sensors to pick up.

"But this isn't really enough. They are also hoping that the multi-million-dollar to Afghans will really pay off. They need that kind of intelligence," said Mr Brookes.

In addition to the leaflets, the offer of the $25m reward is also being spread through word of mouth by US special forces on the ground, according to Pentagon spokeswoman Victoria Clarke.

At present the leaflets are reportedly being dropped between the Taleban's southern stronghold of Kandahar and the eastern city of Jalalabad.

It is thought that Bin Laden may be located somewhere between these two cities.