WASHINGTON - Concerns are growing among US intelligence and military officials that the increasing drone attacks in Pakistans tribal areas are bolstering the insurgency by prompting radicals to disperse into the countrys heartland, according to a media report. Al-Qaeda, Taliban and other militants who have been relocating to Pakistans overcrowded cities may be harder to find and stop from staging terrorist attacks, McClatchy Newspapers reported, quoting the officials. McClatchy, an American publishing company based in Sacramento, California, operates a number of newspapers and websites. The US officials went on to say that the strikes by the missile-firing drones are a recruiting boon for extremists because of the civilian casualties that have prompted widespread anger against the US. Putting these guys on the run forces a lot of good things to happen, said a senior US defence official who requested anonymity because the drone operations, run by the CIA and the Air Force, are top secret. It gives you more targeting opportunities. The downside is that you get a much more dispersed target set and they go to places where we are not operating. US drone attacks may have hurt more than they have helped, said a US military official who has been deeply involved in counter-terrorism operations, according to the report. The official, who requested anonymity because he was not authorised to speak publicly, called the drone operations a recruiting windfall for the Pakistani Taliban. A significant number of bad actors are not where they used to be, but have moved to places where we cannot get at them the way we could, he added. As a result of the drone attacks, insurgent activities are more dispersed in Pakistan and focusing on Pakistani targets, said Christine Fair of the RAND Corporation, a policy institute that advises the Pentagon. So we have shifted the costs. President Barack Obama for now has embraced the drone strikes, which US officials said have killed up to one dozen important Al-Qaeda operatives. If we have a high-value target within our sights, after consulting with Pakistan, we are going after them, Obama said in a March 29 interview with CBS News. Several US intelligence, military officials and independent experts, however, said that they are especially worried by an influx of extremists from the tribal areas into the slums of Karachi. Many militants are thought to have taken refuge among Karachis estimated 3.5 million Pashtuns, the ethnic group comprising the Taliban in Pakistan and Afghanistan, the report said. The whos who of extremism is present in Karachi, Faisal Ali Subzwari, a Sindh government minister, was quoted as saying in the dispatch. There are many areas where police and Rangers cannot even dare to enter. It is a safe haven for those who want a hiding place. US officials have long identified Karachi as the headquarters of the Afghan Talibans fundraising committee, and many top militants were educated at the Binori Mosque, a key center of radical Islamic ideology. A feeder network of militant seminaries in Karachi supplies young suicide bombers, they said. Concerns over blowback from the drone strikes is fuelling a debate in the Obama administration over whether they should be extended from the Federally Administered Tribal Area, the region bordering eastern Afghanistan where Osama bin Laden is thought to be hiding, to Balochistan, the alleged refuge of the Afghan Taliban leadership, US officials were said.