(CNN) An improvised explosive device found near the US embassy in Manila, Philippines, was detonated by police on Monday.

Two eyewitnesses said the device was placed less than 150 meters (500 feet) from the embassy by a person riding in a taxi, Philippines National Police Chief Ronald "Bato" de la Rosa said at a press conference.

"The (device) found near the US embassy today has the same design as the one used in the Davao market blast," De la Rosa said, referring to the September explosion which killed 14 people

He added the police theorized the bomb had been planted by an armed Islamist group.

In a statement to CNN, US Embassy Press Attaché and First Secretary Molly Koscina said the device had been discovered by a "municipal employee."

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