Police Senior Superintendent Alexander Abadinas said the activists burned an effigy of President Arroyo near the Cebu International Convention Center, one of the venues of the annual ASEAN and East Asian summit meetings.
They also set off fireworks near a gasoline station, he added.
Police were considering filing a complaint of illegal assembly against the three activists, Abadinas said.
Philippine National Police chief Director General Oscar Calderon has banned rallies near the summit venues for security reasons.
Meanwhile, retired Gen. Leo Alvez, ASEAN and East Asian summits security chief, denied that safety checks are being neglected at the two conferences.
"Generally I am satisfied but not very satisfied. We still need to make some adjustments," he said. "Nothing is perfect when it comes to security."
Alves, a former Presidential Security Group commander, said he had even received objections from delegates that security was too strict.
"They complained that (at the Shangri-La) everyone is screened and searched... even the ministers," he said. "The only people who will not be screened will be the leaders themselves."
Asked why some security men do not challenge Westerners, Alves said: "I guess that may be a cultural thing. But I agree it is not a good practice."
Some 10,000 police and troops are guarding the ASEAN summit and next Monday’s East Asia summit, which brings in the leaders of Australia, New Zealand, China, India, South Korea and Japan.
At the Cebu International Convention Center this week, some cars have been seen driving through the main gates without having the IDs of occupants checked.
A reporter who walked yesterday into the Shangri-La hotel, where Saturday’s summit will be held, did not pass through a metal detector or have possessions X-rayed.
On Thursday night a media car was allowed to stop in front of the Australian ambassador’s motorcade outside the plush Marco Polo Hotel.
No one was checked or asked to move on.
The press car, which was not displaying its media ID, was then allowed to proceed unchecked to the parking lot.
Security is in place in many locations, with X-ray machines and electronic scanners checking people entering the convention center and other locations. — AP, AFP