Philippine President Rodrigo Duterte has threatened to arrest and send to prison people who refuse to get immunized against Covid-19 despite the relatively small number of vaccines that are available in the country.

"If you don't want to get immunized, I will have you arrested then I'll inject a vaccine into your buttocks," Duterte said in the vernacular.

Duterte has also threatened to inject them with a version of anti-parasitic treatment Ivermectin used for animals.

The Filipino president said his justification for such a harsh measure as arrest was the declaration of a national emergency because of the virus and the dangers posed by unimmunized people as possible "carriers" of the disease, Rappler News said.

The tough-talking Duterte called those who refuse to be inoculated "sons of a whore" and "jerks" and "stubborn" who can spread the virus, according to Philippine online news

Duterte said those who refuse to be vaccinated should just "leave the country" and either go to India or the United States.

The Philippines started its inoculation campaign in March but there have been reports of low turnouts at several vaccination facilities in the country, local media reports said.

As of June 21, health officials had fully immunized almost 2.2 million people, making slow progress toward their goal of vaccinating up to 70 million of the Philippines' 110 million population.

As of Tuesday, the Philippines had reported 1.3 million cases of the virus, with nearly 56,000 still active, officials said.

Meanwhile, there is no legal basis for Duterte's threat to arrest Filipinos who refuse to be immunized, his justice secretary said.

"I believe that the President merely used strong words to drive home the need for us to get immunized and reach herd immunity as soon as possible," Justice Secretary Menardo Guevarra said.

There is no Philippine law that criminalizes the refusal to get vaccinated, or even one that makes Covid-19 vaccines mandatory.