President Mary McAleese and the Taoiseach have issued statements on the attacks in London this afternoon.
Mrs McAleese has sent a message of sympathy to Queen Elizabeth. She said the attacks served no cause, except the cause of evil.
The Taoiseach condemned the attacks as a black mark on society. Speaking in Rome, Bertie Ahern said this had been a terrible and sad day. He said such acts of terrorism would not affect decisions by the G8.
The Minister for Foreign Affairs, Dermot Ahern, expressed his most profound sorrow and concern at the blasts that have devastated public transport in London.
Mr Ahern said while his department was not aware of Irish casualties at this point, the Irish Embassy in London is closely monitoring the situation.
The Dept of Foreign Affairs has set up a helpline for people in the Republic seeking information. They should call 1800 242 548.
Fine Gael leader Enda Kenny sent a message of condolence to the British Prime Minister. Mr Kenny said 'the timing of this outrage is clearly designed to undermine and distract from the efforts of the leaders of the G8 as they focus on tackling the issue of global poverty'.
Worldwide reaction to attacks
Speaking in Gleneagles at the G8 Summit, US President George W Bush said the attacks showed the war on terrorism must continue.
European Commission President, Jose Manuel Barroso, described the attack on London as outrageous and unjustifiable.
He said the European Union would offer every support and assistance to the British authorities in coping with the atrocity.
Mr Barroso, who is in Edinburgh with the G8 Leaders, said it was an attack on the people of Britain, an attack on democracy, and an attack on the fundamental freedoms which go to the heart of the EU.
Russian President Vladimir said the attacks showed the world should unite against international terrorism.
‘Wherever such inhuman crimes occur - in London, in New York or in Moscow - we must unconditionally condemn them and unite all civilised countries in the struggle against international terrorism,’ Mr Putin was quoted as saying by the Interfax news agency.
The Spanish government expressed its solidarity with the British people and government and condemned what it called the 'savage attacks'.
Spanish Prime Minister Jose Luis Rodriguez has put his country's security forces on alert after the blasts. ‘I have given orders to the Interior Minister to activate all alert and prevention systems,’ he said in a televised announcement.
Germany’s Foreign Minister, Joschka Fischer, said terrorism would not prevail and he expressed his country’s ‘horror and disgust’ at the blasts in London.
NATO Secretary General Jaap de Hoop Scheffer said the blasts made clear the need for international action against terrorism.
Pope Benedict XVI condemned the attacks as 'inhuman'.