Two separate explosions ripped through buildings in the Philippines leaving three people injured.

The first explosion occurred inside a fast-food chain in Isabela City in Basilan province on May 30 at around 6:00 pm local time.

Minutes later, the second blast struck a bus terminal about 800 metres away from the first explosion site.

General Domingo Gobway, Joint Task Force Basilan commander, said the first explosion was reportedly caused by faulty electrical wiring. There were no injuries reported, but the establishment sustained minor property damage.

Officials are still investigating the cause of the second explosion, which wrecked a truck parked nearby and injured three civilians - a female vendor and two security guards on patrol who were hit by shrapnel and suffered temporary hearing loss.

Isabela City Disaster Risk Reduction and Management Officer Uso Dan said: 'We don’t know yet what type of explosion this is but we are asking city residents not to panic while we make sure everything is in control.'

The string of recent explosions in the country's southern island of Mindanao prompted the Philippine National Police to heighten security within the capital Metro Manila.

Philippine National Police (PNP) officer-in-charge Lt. Gen. Vicente Danao Jr. said: 'I call on the public not to be alarmed or panic, but to instead remain calm and vigilant. I also encourage everyone to be highly alert and report any suspicious person or behavior, report any unfamiliar face in the neighborhood to the barangay or nearest police station.'

The Isabela explosion is the latest in a series of bombings in the island of Mindanao, which is a known hotbed for terrorists and armed Islamist extremists in the Philippines.

On May 26, two separate bombings involving improvised explosive devices (IED) were reported in Koronadal City in South Cotabato, and Tacurong City in Sultan Kudarat province.

Authorities are still looking into the spate of explosions, and no arrests have currently been made.