The US has launched an extensive media advertisement campaign in Pakistan seeking information on the elusive Osama bin Laden.

US State Department deputy spokesman Adam Ereli said television and radio in Pakistan would air advertisements featuring photos and reward amounts for the capture of the Al Qaeda leader.

The advertisement campaign was launched in the Pakistani newspaper Jang Jan 7 and is now being expanded to the broadcast media, Ereli told a briefing here Monday.

There was no confirmation of media reports that the reward amount for information leading to the capture of bin Laden was being raised from $25 million to $50 million.

"With respect to the rewards, I would note that legislation signed in December 2004 authorised the secretary of state to raise the reward offers under the Rewards for Justice Programme up to $50 million," Ereli said.

"That was legislation authorising us to raise it to that amount. There's no decision made at this time whether to do it."

Asked why the reward had not produced the desired results, Ereli said: "There have been a number of important captures, both through the Rewards for Justice Programme and also through the, I think, aggressive and skilful work of Pakistani and American and other counter-terrorist officials and counter-terrorist forces.

"These sort of things take time. And I think the -- how should I put it -- the trend line is clearly in our favour if you consider the fact that most of the al Qaeda leaders are either dead or in jail.

"There are several very important ones that remain on the run, but they are on the run."

Though there is no concrete evidence of the present whereabouts of bin Laden, some reports have suggested he could be hiding in the area along the Pakistan-Afghanistan border.