Security forces in the Philippines have thwarted a plot to bomb civilian targets on the scale of the Madrid attacks, the president has said.
Arroyo is seeking re-election in May
Gloria Macapagal Arroyo said forces had seized explosives which were to have been used to bomb trains and shopping centres in the capital, Manila.
Several people have been arrested in connection with the plot, she said.
She said the suspects were from the Abu Sayyaf group, which is more usually linked to kidnapping for ransom.
"We have pre-empted a Madrid-level attack on the metropolis by capturing an explosive cache of 80 pounds [36 kg] of TNT
which was intended to be used for bombing malls and trains in
Metro Manila," President Arroyo said on national television.
She said four suspects had been arrested in raids in Manila and follow-up operations were under way.
But the BBC's Kylie Morris in Manila says Ms Arroyo's defence secretary, Eduardo Ermita, admits the only intelligence they have so far with regards to the alleged plan comes from the arrested men themselves.
Mr Ermita said the suspects will also face charges relating to the kidnappings of foreigners in Palawan Province and from Sipadan Island in Malaysia.
He said one of the men has also confessed to the bombing of a ferry in the Philippines in January, which killed more than 100 people and left 100 others missing.
In the wake of the disaster, the government voiced doubt about Abu Sayyaf's claims that it attacked the vessel.
Our correspondent says defence commentators have reacted with scepticism to the news of a planned attack in Manila, suggesting that security issues are making headlines in the midst of the current election campaign in the Philippines.
President Arroyo, a staunch supporter of the US-led war on terror, is seeking a second six-year term in the elections scheduled for 10 May.
The Abu Sayyaf, which is fighting for a separate Muslim state, has been linked by both Washington and Manila to the al-Qaeda network, and both countries class the group as a terrorist organisation.
The Philippine government has deployed thousands of troops in the south of the country where Abu Sayyaf is based in an effort to eradicate the group.