The explosion happened late Friday about five kilometres (three miles) from the heavily guarded complex where Association of Southeast Asian (ASEAN) leaders are meeting and police said they were investigating the possibility it was a revenge assault.
A relative of a 14-year-old boy injured in an attack in the same area by a group of youths earlier in the week had made public threats, police spokeswoman Chief Inspector Kimberly Molitas said.
She described the device as a "homemade pipe bomb" stuffed with low-grade explosives, like the ones used to make firecrackers.
No one has been arrested.
"The incident is not in any way connected to or directed (at) the ongoing ASEAN summit," Ernesto Abella, spokesman for President Rodrigo Duterte, said in a statement.
The Philippines is fighting Islamic militants based in the country's south who have been blamed by police in the past for deadly bombings as well as kidnappings.
Of the 14 people hurt, six were treated for minor wounds and sent home, while eight others remain in hospital, two of them with serious injuries, Molitas said.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)
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