WASHINGTON, Feb 29: Osama Bin Laden crossed into Pakistan on Feb 27 and is closely guarded by Al Qaeda and Taliban fighters disguised as a Pakistani tribesman, US media reported on Sunday.

The reports said Bin Laden "is currently hiding" in a remote area in South Waziristan near the Afghan border. On Saturday, both US and Pakistani officials denied a Teheran Radio report that the Al Qaeda leader was already in Pakistan's custody and would be brought to the United States close to the presidential elections scheduled in November this year.

But when a Pentagon spokesperson was asked to comment on the reports that Bin Laden was seen in Waziristan and that US and Pakistani authorities had stepped up their efforts to catch him, she said: "Yes, we have seen the reports."

Asked to confirm or deny the report, she repeated: "I told you, we have seen them." The reports said recent US military advances in southern Afghanistan forced Bin Laden and his Taliban supporters to quit their hideouts in Afghanistan. The reports also said more than once US military search teams had come close to these hideouts.

Such close encounters, the reports said, convinced Bin Laden and his protectors to seek refuge in the tribal areas of Pakistan and on Feb 27 they crossed into southern Waziristan.

But the reports suggest that Bin Laden and his followers are not safe in Pakistan either because US and Pakistani forces have already marked the area where they believe he is hiding. They are, however, reluctant to launch a full assault because of hundreds of Pukhtun fighters protecting the Al Qaeda leader.

Pakistan is particularly concerned that any offensive that leads to a large number of Pukhtun deaths could have very negative political consequences for the government in Islamabad, the reports said. Instead of a direct assault, Pakistan has urged the Americans to isolate Bin Laden and his fighters by severing food and water supplies.