The British Prime Minister today vowed that those responsible for the "hideous and foul" terrorist attacks on America would be brought to justice.
In an emergency statement on the crisis, Mr Blair told the Commons that once the perpetrators were identified "appropriate action" would be taken.
"It will be determined, it will take time, it will continue over time, until this menace is properly dealt with and its machinery of terror destroyed," he pledged.
"By their acts these terrorists and those behind them have made themselves the enemies of the entire civilised world."
Flanked by the Deputy Prime Minister Mr John Prescott and Foreign Secretary Mr Jack Straw, Mr Blair acknowledged that "different shades of opinion" would be aired in the chamber today.
"But let us unite in agreeing this: what happened in the US on Tuesday was an act of wickedness for which there can never be justification.
"Whatever the cause, whatever the perversion of religious feeling, whatever the political belief, to inflict such terror on the world, to take the lives of so many innocent and defenceless men, women and children can never ever be justified.
Mr Blair outlined the "sickeningly familiar" events that led to the collapse of the World Trade Centre and expressed admiration for the "selfless bravery" of the emergency services.
"As we speak, the total death toll is still unclear, but it amounts to several thousands," he said.
"Because the World Trade Centre was the home of many big financial firms, and because many of their employees are British, whoever committed these acts of terrorism will have murdered at least 100 British citizens, maybe many more.
"Murder of British people in New York is no different in nature from their murder in the heart of Britain itself. In the most direct sense, therefore, we have not just an interest but an obligation to bring those responsible to account."
To underline the scale of the tragedy, Mr Blair recalled past atrocities like the Omagh bombing and Lockerbie explosion.