Hackers in Pakistan have declared a cyber jihad on the US and Britain, only days after the FBI issued a warning predicting as much.

Earlier this week, Pakistani hacker group GForce defaced the website of the National Oceanic and Atmospheric Administration Center, part of the US Department of Commerce, leaving a message promising more of the same type of attacks.

The FBI warning, issued last Friday, said: "Many Muslim groups around the world have significant experience in launching sophisticated and sustained cyber attacks.

"In this context, a variety of pro-Muslim hacker groups, such as the G-Force Pakistan, The Pakistan Hackerz Club or Doktor Nuker, could use these tactics against the US and its allies."

The GForce defacement carried the message: "In a few days we will hit major US military and major British websites, we will jeapordise their internel [sic] security."

The group also threatened that it has "some very high confidential US data that will be given to the right authorities of Al-Qaeda, remember if you give us peace you will get peace, is it that difficult?".

Although the hackers claim to condemn the attacks on the US, they also claim to "stand by Al-Qaeda. Osama bin Laden is a holy fighter, and whatever he says makes sense."

The group also warns of an "Al-Qaeda Alliance Online" involving other hacker groups which it said will start attacking sites "soon" in a bid to convey its message.