The explosion occurred in a bustling part of the city and close to one of its top hotels that is popular with tourists and business people, city spokeswoman Catherine dela Rey said.
“There was an explosion but, as to what caused it, it is still under investigation,” dela Rey said.
“Ten people died on the spot, at least 30 injured.”
Davao is the biggest city in the southern Philippines, with a population of about two million people. It is about 1,500 kilometres (930 miles) from the capital of Manila.
Duterte had been mayor of Davao for most of the past two decades, before winning the national elections in a landslide this year and being sworn in as president on June 30.
Reported explosion in Davao City Friday night left a number of people dead and several others wounded…. https://t.co/AZY5MI7O1y
— DavaoCity Government (@DavaoCityGov) September 2, 2016
Islamic militants and communist rebels have carried out deadly attacks in Davao, however authorities stressed it was too early to determine the cause of Friday’s blast.
“Right now, we cannot yet give definite answer to questions as to who is behind this as we are also trying to determine what really exploded,” the president’s son and Davao vice mayor, Paolo Duterte, said in a statement.
“Let us pray for the victims of this unfortunate incident, especially for those who died. Let us pray for those who are being treated in different hospitals and pray for their quick recovery.”
The vice mayor confirmed there were “at least” 10 people who died.