The authorities are investigating Sunday's explosion at Mindanao State University, the regional police director, Brigadier General Allan Nobleza, told reporters, adding that one angle being pursued was possible revenge by pro-Islamic State militants.
The blast occurred in Marawi, a city besieged by Islamist militants in for five months in 2017.
Taha Mandangan, the security chief of the sprawling state-run campus, said at least two of the wounded were fighting for their lives.
"This is clearly an act of terrorism. It's not a simple feud between two people. A bomb will kill everybody around," Mandangan told the Associated Press.
Regional police director Brigadier General Allan Nobleza said investigators were assessing if the explosion was caused by a homemade bomb or a grenade, and if the attack was connected to 11 militants killed in a military operation the day before in Maguindanao del Sur province.
"I condemn the violent bombing incident that transpired this morning," Lanao del Sur Governor Mamintal Adiong Jr said in a statement.
"Terroristic attacks on educational institutions must also be condemned because these are places that promote the culture of peace."
Mindanao State University is "deeply saddened and appalled by the act of violence that occurred during a religious gathering," it said in a statement on Facebook.
"We unequivocally condemn in the strongest possible terms this senseless and horrific act."
The university said it was said it was suspending classes until further notice.
The southern Philippines is the homeland of minority Muslims in the predominantly Roman Catholic nation and the scene of decades-old separatist rebellion.
The largest armed insurgent group, the Moro Islamic Liberation Front, signed a 2014 peace deal with the government considerably easing decades of fighting. But a number of smaller armed groups rejected the peace pact and press on with bombings and other attacks while evading government offensives.
with AP
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