Calinisan said there are "lawless elements determined to embarrass the government and get even with the police and the military," adding that these people belong to communist and opposition groups.
But opposition leader Edgardo Pamintuan, former mayor of Angeles City, debunked Calinisan’s claim that the opposition could be behind terroristic attacks against innocent civilians.
"The opposition is not morally capable of such lawlessness. No way," he said.
Pamintuan urged the public to stay focused on the impeachment trial of President Estrada which resumes today in the Senate.
The leftist Bagong Alyansang Makabayan (Bayan), for its part, said in a statement that "no one else but the Estrada regime should be held accountable for the spate of bombings" in Metro Manila.
Bayan secretary-general Teddy Casiño said, "It is also in Mr. Estrada’s interest that fear pervades the entire nation to preempt the brewing first quarter storm of nationwide protests demanding his ouster."
Calinisan said he has ordered police units throughout Central Luzon to keep a tight watch on vital government installations, particularly the ammunition depot in Bataan.