President Rodrigo Duterte slammed on Wednesday former Colombian President Cesar Gaviria by calling him an "idiot."

"To tell you frankly, they said Columbia has been lecturing about my...that idiot," said Duterte in a speech during the 115th anniversary of the Bureau of Customs in Manila.

He did not mention Gaviria's name but he was apparently referring to the former Columbian leader, who criticized Duterte's bloody war on illegal drugs.

Gaviria, in his article in the New York Times, said war on drugs could not be won through violence, citing the Columbian experience where it became bloody and yet they did not succeed.

Duterte reiterated the serious effect of methamphetamine hydrochloride or shabu, the top consumed illegal drug in the country, on its users compared to using cocaine, heroine or marijuana.

"Cocaine also heroin (are) not really… but cocaine is more or less marijuana, it's better, you can still communicate. But with the shabu...the fact alone that it is mixed using (car) battery water will give you an indication of what’s going to happen inside your brain," he said, calling shabu users as "slaves."

Presidential Spokesperson Ernesto Abella, in a statement, said the Palace respects Gaviria's statement that Colombia’s experience of "war against drugs" cannot be won by the armed forces and law enforcement agencies alone.

"The Philippine President rightly understood the same insight when he began to address not just crime and illegal drugs but also broadened government efforts into a public health issue," he said.

The second phase of the President’s anti-drug campaign focuses on the treatment and rehabilitation of drug dependents, he noted, adding, "more than a national security problem, the proliferation of drugs in the country has been regarded as a health pandemic."

He cited that a 2,500-patient capacity Mega Drug Abuse Treatment and Rehabilitation Center (DATRC) in Fort Magsaysay, Nueva Ecija was inaugurated last November.

Another drug rehabilitation center, the Residential Treatment and Rehabilitation Center (RTRC) in Agusan del Sur -- the first to open in a military camp in Mindanao ? was also opened last year, he said.

He added the Philippine Health Insurance, the government’s national health insurance program, now covers a two-week drug rehabilitation program reserved at P10,000 per member.

"It is unfortunate that international attention to the drug war in the Philippines centers on drug-related killings rather than the breakthroughs of the campaign. However, we appreciate the ex-Colombian president's concerns and we encourage our people to see our situation in the light of comprehensive nation-building," Abella said.

Over 7,000 drugs suspects have been killed since the war on drugs was launched seven months ago. Of those who died, about 2,500 were during the police operations. Celerina Monte/DMS