The Taoiseach has offered the "heartfelt sympathy" of the people of Ireland to those affected by the London bombings.
Speaking after signing a book of condolences opened at the British Embassy at Ballsbridge in Dublin, Mr Ahern said the last week was "an enormously tragic one for our neighbours".
The Taoiseach branded the attacks as "callous, indiscriminate and brutal" and added that they had caused enormous pain to so many people. He pledged the Government would continue to co-operate and move to fight terrorism through all the mechanisms available.
Meanwhile, he said he had no further information about Irish people who may have been caught up in the blasts.
The Irish Department of Foreign Affairs is still expressing concerns for an Irish passport holder after the bombings.
A spokeswoman said they were still trying to establish the whereabouts of a woman, with dual Irish and New Zealand citizenship, who had recently moved to Britain.
An Irish man remains in hospital in London undergoing treatment for injuries suffered in the attacks. A number of other Irish nationals have been released from hospital.
The Mayor of Armagh, John Campbell , wrote to the Mayor of London Ken Livingstone expressing the sympathies of the city.
Mr Campbell branded the bombings as "wicked, indefensible acts" which had appalled all right-thinking people.
He added: "We share the anger which will be felt across London but our thoughts and prayers are first and foremost with those who were caught up in this terrifying ordeal."
PA