The threat from terrorism and weapons of mass destruction remains high, the prime minister has said.

Answering questions from journalists on Thursday in the wake of bombings in Morocco and Saudi Arabia, Tony Blair said that al Qaeda has demonstrated its "totally evil intent" towards Britain.

The group led by the still uncaptured Osama bin Laden is also thought to have issued new instructions for further attacks around the world, prompting America to increase its security warning level.

Blair said that "we have good evidence from what al Qaeda is doing around the world that they have a totally evil intent towards us, towards any country frankly".

"Who would have said that Morocco was in the forefront of the campaign against al Qaeda or anything to do with the military action in Iraq and yet these people are willing to kill totally innocent people in whatever part of the world they decide to take their terrorist campaign."

The public should remain alert to the threat both at home and abroad, the prime minister cautioned.

"In respect of this country, all I can say is that we have increased levels of vigilance precisely because we can see very obviously the threat that al Qaeda pose," he said.

"We continue to act on any specific pieces of intelligence we have, but I think it is frankly almost a statement of the obvious with what is going on in the world that we have to make sure we are taking every single precaution, and we do.

"The difficulty with these people is that they are prepared to kill any number of innocent people without any compunction whatever."

State sponsored terrorism also remains a concern, Blair warned, but he chose his words carefully when pressed on his alliance with Washington over the US-branded "axis of evil" now reduced to just North Korea and Iran.

"There are real concerns, there are concerns about North Korea, there are concerns about Iran, and we are raising those concerns," he said.

"The issue is not for me whether we stick with the White House or not, the issue for me has always been my own country's national interest.

"The reason why I was absolutely solidly with the America over Iraq is because I believe that to be in the interest not just of America but of Britain and the wider world."

The prime minister declined to be drawn on whether he would join the US in any further pre-emptive military strikes, but he did insist that the two rogue states would have to be tackled.

"I'm not going to get drawn into speculating what we may or may not do further down the path but I've always said that there are real issues to do with terrorism and weapons of mass destruction that we have to confront," he said.

"How we confront them is another matter and there are all sorts of different ways of confronting them.

"But we would be very foolish as a country and as a world if we simply shrugged our shoulders and left them alone."