The embassy asked US citizens to be “aware of your surroundings” and report any “suspicious package” to authorities.

The United States on Thursday warned its citizens in the Philippines to remain vigilant after local authorities said they had foiled a plot by an Islamic militant group to bomb the nation’s capital.

“The Embassy wishes to remind all US citizens to remain vigilant and maintain an appropriate level of personal security in all circumstances,” the US mission in Manila said in a security message posted on its website.

The embassy asked US citizens to be “aware of your surroundings” and report any “suspicious package” to authorities.

Philippine authorities did not issue any similar alert.

But presidential communications secretary Herminio Coloma said in a statement following the US embassy warning that security officials were “aware of the situation” and were “not letting their guard down”.

Police had previously said they arrested Ricardo Ayeras, one of the founders of the Rajah Solaiman Movement, and two companions at a checkpoint in a northern Manila suburb on Sunday.

“(According) to intelligence reports (the) suspects are to do bombings in Metro Manila,” Chief Superintendent Richard Albano, the head of police in the northern districts, said in a statement on Wednesday.

Albano said the three men were armed with a hand grenade and carried fake identification cards when they were flagged down by police while aboard a single motorcycle.

However he gave no further details about the alleged plot. Police and military officials declined to comment on Thursday.

The Rajah Solaiman Movement, named after a 17th century Muslim ruler of Manila, is a small group of Christian converts that is most notorious for a failed plot to bomb the US embassy in 2005.

The plan was foiled when a police raid turned up large quantities of explosives at the group’s northern Manila hideout.

Ayeras, 41, uses the alias Abdul Karim Ayeras after converting to Islam.

Police previously said the Rajah Solaiman Movement had received bomb-making training by the Abu Sayyaf, an Al Qaeda-linked group blamed for the country’s deadliest terrorist attacks.

Ayeras had been arrested three times between 2007 and July this year over his alleged involvement in the 2003 bombing of a southern Philippine airport that left one person dead and several others wounded.

However, the judiciary ordered him released each time due to insufficient evidence, Albano said on Wednesday.