According to the foreign news agency Al Jazeera, one of the blasts is being described as a suicide bombing which was carried out by a female suicide bomber.
The head of the Philippine Red Cross, Richard Gordon, said the bomber struck shortly after noon in Solo, the capital of one of the country's southern provinces.
Richard Gordon, a senator, said a motorcycle with an IED exploded near an army truck.
According to news reports, Maj. Gen. Corlito Vanluan said authorities were cordoning off the area after the first blast, which was reportedly carried out by a female suicide bomber, killing one person.
If confirmed, it would be the fourth known suicide attack in the country.
At least 24 soldiers were injured in the two attacks.
The bomber struck shortly after noon in front of a Catholic church, killing more than 20 people, according to the state broadcaster.
Pictures posted by the broadcaster on social media showed debris and bodies near a military vehicle. No one has yet claimed responsibility for the attacks. Philippine Police Chief General Archie Francisco Gamboa said in a statement that he had ordered an investigation into the incident. He said all perpetrators would be punished.
Solo is said to be the stronghold of the Abu Sayyaf Group, an armed group that has allied itself with ISIS. The group is known for kidnappings, robberies and bombings.
Two similar blasts outside a church in the Philippines in January last year killed at least 20 people.
People were worshiping inside the Roman Catholic Church when the first explosion occurred outside the synagogue, followed by piles of corpses and wounded everywhere.
While law enforcement and volunteers were coming to help the injured, another explosion occurred inside the car park, causing extensive damage.
According to military sources, the second bomb was planted on a motorcycle parked in a car park outside the church.
