ROME (AP) -- The whole of Europe was on alert Thursday following a series of bombings in London, Italian officials said, while security officials were assessing Italian security and Italy's airports raised their alert level to a maximum.
Italy's European commissioner called the explosions in central London on Thursday a terrorist strike against Europe.
''What has happened is the tragic confirmation that terrorism strikes once more at the heart of Europe,'' said Franco Frattini, Europe's commissioner for justice and home affairs, in comments reported by Italian news agencies and confirmed by his office.
''It's necessary to immediately activate coordination between intelligence and police services, and offer England all the help possible,'' Frattini said.
In an address to the Italian parliament, Interior Minister Giuseppe Pisanu said Italy was not alone in calling a state of alert, but that all of Europe was stepping up vigilance. Italian security officials were meeting to assess the situation and decide what measures could be taken, the ministry said.
A group calling itself ''The Secret Organization of al-Qaida in Europe'' posted a claim of responsibility for Thursday's blasts on the Internet, saying they were in retaliation for Britain's involvement in Iraq and Afghanistan.
The statement also threatened attacks in Italy and Denmark, warning those countries ''and all crusader governments that they will receive the same punishment if they do not withdraw their troops from Iraq and Afghanistan.''
The head of the Italian parliamentary commission overseeing secret services, Enzo Bianco, said he had no information to ascertain the reliability of the claim.
Other countries that have announced increased security at shopping centers, airports, railways and subways include the Czech Republic, Hungary, Russia, the Netherlands, France and Spain, which was hit by deadly al-Qaida-linked bombings in Madrid last year. Belgium's prime minister asked emergency response officials to assess security in the Belgian capital, Brussels, which houses European Union and NATO headquarters.
Bianco said the London attacks appeared more sophisticated than the ones that hit Madrid on March 11, 2004.
''The operation is much more complex, the attack requires a good knowledge of the territory, and a residency in the territory for months, if not years,'' he said.
Italian airports were functioning on maximum alert, the civil aviation authority said. National airline Alitalia said its schedule of flights for London airports was not changed, however, following the blasts.
Frattini said in separate comments that he was in constant contact with British authorities and with his commission office, and that the European Commission would meet next week to discuss new rapid reaction measures against terrorist attacks.
Italian President Carlo Azeglio Ciampi sent a message to Queen Elizabeth II, expressing ''consternation and horror'' at the ''bloody attacks,'' and expressed condolences for the victims.
Premier Silvio Berlusconi, who was attending the G-8 summit in Scotland, had been in touch with Pisanu through his spokesman and was informed of the situation following the blasts in London, Italian diplomatic sources at the summit said.
The Italian Foreign Ministry said it was checking whether their were any Italian casualties.
Italy's parliament suspended work in both its houses Thursday as a sign of solidarity after the explosions were reported.
The Italian lower house suspended work for 15 minutes following news of the explosions, and also held a minute of silence, while the Senate called off its session until the afternoon, parliamentary officials said.
The Milan stock exchange said it had no plans to close.
