MANILA, Philippines (Updated 12:51) — Agencies involved in the government's campaign against illegal drugs believe President Rodrigo Duterte "has basis" to say that there are now seven to eight million drug users in the Philippines, up from 4 million claimed in 2017.

The figure of four million was itself higher than an estimate by the policy-making Dangerous Drugs Board of 1.7 million users based on its survey.

Senior Superintendent Bernard Banac, Philippine National Police spokesperson, said Thursday at the "Real Numbers" press briefing that the president "has wide access of information and unlimited sources of intelligence," which, he said makes the PNP inclined to say there is basis for the estimate.

Alamin ang tunay na numero tungo sa tunay na pagbabago.#RealNumbersPH pic.twitter.com/Oi5RITBKdn — Radyo Pilipinas (@radyopilipinas1) February 28, 2019

RELATED: Duterte hikes drug use figure after claims of 'successful' drug war

On Wednesday, Director General Oscar Albayalde, PNP chief, said that the police do not have a verified number of drug users in the Philippines, stressing that "an estimate is just an estimate."

He said that "even the three million that has been declared before, we're not sure if it's really three million. Maybe what the president sees is despite our war on drugs, he has been saying that it is chilling because we still see people using drugs and there are still those who supply even down to the barangay level."

In 2017, Duterte claimed there were around 4 million drug users in the Philippines, a figure that contradicted data from the policy-making Dangerous Drugs Board that estimated the number at 1.7 million drug users.

Duterte later fired the chairman of the DDB for "contradicting the government."

READ: Are there 4 million drug addicts in the Philippines? | 4M drug users 'in the realm of possibility,' DDB insists

cont... Alamin ang tunay na numero tungo sa tunay na pagbabago.#RealNumbersPH pic.twitter.com/TnvZuvSPs7 — Radyo Pilipinas (@radyopilipinas1) February 28, 2019

Banac said Thursday that the actual number of drug users may be higher than the DDB's figure since some users "have not come out and admitted they are drug users."

He said that some users only occasionally use drugs (patikim-tikim lang) and do not consider themselves drug users.

"Marami po 'yan. Marami 'yan," he said.

The DDB survey counted respondents who have used drugs even once as drug users.

'Drug figures increase with successful operations'

The Philippine Drug Enforcement Agency, lead agency in the campaign against illegal drugs, also backed the new estimate, stressing "the president has a wealth of access to information."

PDEA spokesperson Derrick Carreon said that the number of drug users may be adjusted because of the number of arrests and surrenderees in the government's vigorous campaign. "The four million was a conservative estimate. Definitely this will reflect a bigger data," he said.

National Bureau of Investigation Director Ferdinand Lavin, who was also at the briefing, said "when the president first made the estimate when he assumed office in 2016, the basis for the estimate was limited in number."

He said that "drug operations are improving, and with the arrests come additional information." He added "arrested addicts that provide information" lead to the adjustment of drug numbers.

Lavin said that estimates are only meant to guide policy, and are not meant to be a definite number.