Inconceivable Osama didn't have support system in Pakistan: US

The US today said it was "inconceivable" that Osama bin Laden had no support system inside Pakistan and the American adminstration is investigating how the al Qaeda chief was able to hold on in the country for so long.

While refusing to speculate on what kind of support Osama might have had in Pakistan, counter terrorism chief John Brennan did not rule out the possibility of the terrorist having official backing.

"It is inconceivable that bin Laden did not have support system in the country that allowed him to remain there for extended period of time," Brenann told reporters at a news conference at the White House.

Bin Laden was killed early this morning in Pakistan's Abbottabad city, 120km from the capital Islamabad.

"We are going to pursue all these to find out what kind of support system and benefactors that bin Laden might have had," he said.

"We are looking right now at how he was able to hold up there for so long and whether or not there was any type of support system within Pakistan that allowed him to stay there," he said.

Brennan said the fact that bin Laden was found so close to the capital "raises questions".