First minister Henry McLeish contacted the US consul in Edinburgh to express the sympathy of the Scottish people.
'The prime minister has today spoken for the United Kingdom - and for all Scots - when he expressed his horror at the terrible, shocking events in the United States of America.
'I have today written personally to the Liane Dorsey of the American consul in Edinburgh to express on behalf of the Scottish executive - and the Scottish people - our condolences.
'Innocent people have lost their lives today and our thoughts and our sympathy are with the people of America and President Bush at this time.
'The prime minister has spoken for all of us when he said democrats that we must unite to oppose the evil of terrorism.
'It is difficult to find words to express your feelings in the face of an incident like this.
'The Scottish cabinet met today but it was a brief meeting and the thoughts of all those around the table were with the people of America.'
Earlier prime minister Tony Blair told delegates at the TUC conference in Brighton:
'There have been most terrible, shocking events taking place in the United States of America within the last hour or so, including two hijacked planes being flown deliberately into the World Trade Centre. I'm afraid we can only imagine the terror and the carnage there, and the many, many innocent people that will have lost their lives.
I know that you would want to join with me in sending the deepest condolences to President Bush and to the American people on behalf of the British people at these terrible events. This mass terrorism is the new evil in our world today. It is perpetrated by fanatics who are utterly indifferent to the sanctity of human life, and we the democracies of this world are going to have to come together to fight it together and eradicate this evil completely from our world.
Delegates, I hope you will understand that I don't believe it would be appropriate to carry on the speech that I was going to give to you today. I know I have issued copies of the speech, we will make sure that all delegates get copies of the speech; but I think it inappropriate to give that speech now, here. I will obviously want to carry on the discussions that we've had about the issues that concern us. I will now return to London, and once again I thank you for your indulgence here. I am very, very sorry that it has turned out the way that it has. But I know that, as I say, you would want to join with me in offering our deepest sympathy to the American people and our absolute shock and outrage at what has happened.'
The Foreign and Commonwealth Office have issued an emergency number for those worried about friends or relatives in the United States: 0207 008 0000
Statement from the Welsh first minister on terrorist attacks in America:
'Having only just returned from the USA, I am appalled and revolted by this carnage inflicted on innocent people by these barbaric acts of terrorism.
'On behalf of the people of Wales I want to send the president and people of America our deepest condolences and sympathy. I am contacting the US consular office in Cardiff with the same message.
'Terrorism takes no prisoners but in the end wins no wars.'