Police on Wednesday said they have in custody two persons of interest in the alleged bombing attempt near the US Embassy in Manila.

National Capital Region Police Office (NCRPO) regional director Chief Supt. Oscar Albayalde confirmed that at least one suspect was invited for questioning in Bulacan province after an informant tipped off authorities.

"Mayroon po tayong naging informant, may nagmagandang loob... At of course iyung intelligence gathering natin, pinagtagpi-tagpi po natin iyan base rin po doon sa paglabas ng cartographic o composite sketch na inilabas natin kahapon," Albayalde told radio DZMM.

A separate ANC report said one person of interest, a merchant of cellphones, was taken into custody in Caloocan City Tuesday night while the other was taken into custody in Bulacan Wednesday.

The person of interest from Bulacan hails from Marawi, police said.

Both persons of interest are Muslims but have no proven link so far to the Mindanao-based Maute terror group.

"Sila po ay Muslim pero iyung talagang pag-amin na sila ay member ng Maute Group, iyan ay iniimbestigahan pa natin. Hindi pa po talaga sila nagsasalita," Albayalde said.

The two men are now under custodial investigation at Manila Police District headquarters.

The bomb found Tuesday at a trash can along Roxas Boulevard resembled an improvised explosive device (IED) that detonated in a Davao City night market in September, killing 14, according to police.

Philippine National Police chief Director General Ronald "Bato" dela Rosa said the bomb was left by a suspect riding a white taxi and who was wearing a shirt, black pants, and leather shoes when he left an explosive.

Police released a sketch of the suspect described as fair-skinned, around 5"5' in height, aged more or less 44 to 45 years, and with a weight of 60 to 65 kilograms.

Dela Rosa will give an official statement on their interrogation of the two persons of interest on Friday, Albayalde said.

• Timeline of deadly bomb attacks in Manila