"We have received information, but these are not validated threats,'' military spokesman Lt. Col. Bartolome Bacarro said.
"We are not discounting the possibility that some... threat groups would take advantage of the ASEAN summit, but security forces... are all pepared and all contingencies have been taken into consideration."
Civilians will be banned from carrying guns in summit venues and flights will be restricted over those places.
Security officials suspect that militants could strike elsewhere in the country, to thwart security measures in Cebu.
A government report cited Indonesian-based Jemaah Islamiyah (JI) and the Philippine-based Abu Sayyaf and Moro Islamic Liberation Front as possible threats at the summit.
JI is widely believed to have carried out several deadly attacks in Indonesia, including the 2002 nightclub bombing in Bali that killed 202 people.
The Abu Sayyaf has conducted domestic attacks, including a 2004 ferry bombing that killed 116 people.
Some Western intelligence agencies suspect that Abu Sayaff might have links with JI.
The ASEAN summit will run from December 10-14