At least 12 people were killed and 60 injured in the explosion in the south of the country, officials in Manila said on Friday.

"Based on initial investigation, police found a shrapnel from a mortar-based improvised explosive device," Communication Secretary Martin Andanar said in a radio interview.

Davao police station commander Milgrace Driz also said that many of those injured suffered shrapnel wounds.

"Our explosive ordnance team is already in the area to confirm the cause of the blast," she told the Reuters news agency by telephone.

While no one has claimed responsibility for the suspected attack, presidential spokesman Ernesto Abella urged the public to "refrain from reckless speculation and avoid crowded places."

"There is no cause for alarm, but it is wise to be cautious," he said.

Duterte unharmed

The southern city of Davao is the stronghold of Filipino President Rodrigo Duterte, who had served as its mayor for most of the past two decades. Duterte was in the city at the time of the blast, but was not harmed, officials said.

The explosion damaged the street market in front of the luxurious Marco Polo hotel, which is often visited by the president. Both communist rebels and Islamist terror groups have previously carried out deadly in attacks in the city of around two million people.

The president's son, Paolo Duterte, also confirmed that his father was safely waiting at a police station.

"Right now, we cannot yet give a definite answer to questions as to who is behind this as we are also trying to determine what really exploded," Paolo Duterte, who serves as Davao's vice mayor, said in a statement.

The government is currently locked in a struggle with terror groups such as Abu Sayyaf and Maute.

At a press conference earlier on Friday, President Duterte shrugged off rumors of a plot to assassinate him, saying such threats were to be expected.

dj/kms (AFP, Reuters, dpa)