A suspected motorcycle bomb wounded five people at a drugstore in the southern Philippines on Tuesday, police said.
One of the five casualties, a seven-year-old boy, is in critical condition from the early afternoon blast, said Superintendent Roberto Badian, the police chief of the southern city of Cotabato.
"It appears the bomb was triggered by a cell phone," Badian told reporters.
No group has claimed responsibility, he added.
The city has in the past been a target of Muslim separatists and Islamist militants linked to the al Qaeda movement whose global leader Osama bin Laden was killed in a US military raid in Pakistan on May 2.