A statement claiming to come from al-Qaeda has warned of imminent terrorist attacks in Britain and other countries.
Security has increased in the UK
The statement e-mailed to Arab news organisations on Wednesday night was signed by a group which said it carried out attacks in Madrid and Istanbul.
It warned the UK, Australia and Saudi Arabia that a "brigade of death" was targeting them and other countries.
But it also said it was freezing its operations in Spain as a reward for the new government's stance on Iraq.
Spain's prime minister-elect, Jose Luis Rodriguez Zapatero, has said he will pull Spain's 1,300 troops out of Iraq unless the UN intervenes.
BBC security correspondent Frank Gardner said the message included a poem in praise of Osama bin Laden and was signed by the Abu Hafs al-Masri Brigades.
They claimed responsibility for the attacks in Madrid, which killed 201 commuters last week, and bombings in Istanbul and Iraq.
But the group lost credibility last year when they falsely claimed responsibility for the power cuts in the US.
The Metropolitan Police commissioner Sir John Stevens said this week that a terrorist attack on the English capital was inevitable.
British Transport Police (BTP) has said hundreds more police officers will be seen at British stations to reassure passengers and improve security.