Osama Bin Laden's al-Qaeda network is now working closely with Middle Eastern and other extremist groups after most of its members fled the US-led invasion of Afghanistan, it is reported.

As a result US efforts to combat the group may have become more complicated, intelligence officials say, according to the New York Times.

"What we are seeing now is a radical international jihad that will be a potent force for many years to come," one official told the newspaper.

Another report says Friday's car bomb attack in Karachi, Pakistan, which killed 11 people was carried out on Bin Laden's instructions.

Tactical alliances

The New York Times says at least seven middle-ranking al-Qaeda members are now playing a far greater role in organising attacks around the world.

They include a number of Egyptians as well as a Saudi and a Kuwaiti national.

Has the US bombing made it harder to track down al-Qaeda?

The paper says officials of America's FBI and CIA believe the men have been making tactical alliances with extremists in Egypt, Algeria, Pakistan and other countries.

A report in the Washington Times from Morocco - where three al-Qaeda suspects are being held - backs up some aspects of the New York Times report.

The three men, all Saudi nationals, were arrested last month in connection with a plot to attack American and British naval ships in the Straits of Gibraltar.

They have now told their Moroccan interrogators that Bin Laden ordered his fighters to "disperse across the globe to attack" American and Jewish interests, the Washington Post says.

Moroccan officials say Friday's deadly bomb attack in Karachi, Pakistan, as well as the April bombing of a Tunisian synagogue that killed nearly 20 people, were carried out as a result of Bin Laden's instructions, according to the Post.

The report casts further doubt on claims that Bin Laden was killed during the American bombardment of Afghanistan.