The explosion occurred just before 10pm last night at an empty house in The Boltons, an expensive residential area of west London. There were no immediate reports of any injuries, police and emergency services said.
However, windows were blown out at the house and in neighbouring buildings. Police cordoned off surrounding streets.
Local resident Winnie Gordon Strauss, who was out walking her dog when the bomb went off, said: "I've still got glass in my hair."
The anonymous telephone call received by the news agency in London, claiming to be from the IRA, was received about half an hour before the first report of a blast.
Last night's explosion happened less than half a mile from the site of a similar blast on March 8. Then, a bomb was placed in a rubbish bin outside the gates of Brompton Cemetery, near the Earl's Court Exhibition Centre. No one was injured, but there was damage to property and cars.
The blast came as politicians on all sides were desperately trying to restore some momentum to the peace process after the IRA's decision to end its year-long ceasefire. But continuing dissatisfaction with the Government's plans for elections leading to all-party talks in the province saw the various Northern Ireland parties attempting last night to modify the proposed mechanism for the elections.
The Ulster Unionist Party, Democratic Unionists, SDLP and UK Unionist MP, Robert McCartney, all intend putting down amendments to the legislation covering the election and all-party talks.
The new Elections Bill was formally introduced in the Commons yesterday and the Government plans to rush it through Parliament and have it on the statute books early next month, in time for the poll to go ahead on the planned date of 30 May.
Ulster Unionist leader David Trimble said: "The system is unnecessarily complex and has a number of absurdities in it. I think we are going to have to spend some time at Westminister over the next few days trying to improve it."
The Rev Ian Paisley has already announced he will be putting down amendments.
The SDLP is also seeking changes and will await the final shape of the Bill before deciding whether to stand for the elections.
Meanwhile, Gerry Adams demanded that Sinn Fein be admitted to the all- party talks due to start on 10 June, whether or not the IRA calls a new ceasefire, a prospect looking increasingly remote after last night's bomb attack.
Sinn Fein is waiting to see what the SDLP decides about standing at the poll. It would prefer to boycott the event but is almost certain to stand if the SDLP decide to.
Mr Adams said: "If Sinn Fein contests the forthcoming election, those who vote for our party should have exactly the same rights as other sections of the electorate. Whatever the IRA does, Sinn Fein's electoral mandate cannot be ignored by the British Government."
However, ministers continue to insist that Sinn Fein will not be granted entry to the talks unless there is a new, clearly called ceasefire.Reuse content