MANILA - Philippine President Rodrigo Duterte suffers from back pains and migraine headaches, he has said in comments about his health, but a spokesman was quick to dismiss the ailments as not being serious.

Duterte also said he suffered from Buerger's disease, a cause of blockages in the blood vessels, associated with smoking during his youth. He no longer smokes and drinks.

• Duterte: I'm dying, what's your problem?

The 71 year-old leader, the oldest to be elected president in the Philippines since the post-war period, said he did not fear being removed from power, or assassinated, because of opposition to the rising death toll in his anti-drugs campaign.

Since July 1, about 5,000 people have died in Duterte's war on drugs, a key plank of his May election campaign. Police say 2,004 have been killed by officers in self-defense, with another 3,060 killings "under investigation".

"Oust me, good, assassinate me, better, I have this migraine everyday," he told a meeting of business leaders late on Monday.

"I have a lot of issues with my spine. What I have is really Buerger's disease. It's an acquired thing that you get from smoking, because of nicotine."

Doctors had advised surgery on his spine, he said, but his wife, a nurse who used to work in the United States, did not agree because "a lot of operations for the spine went wrong".

He added, "If you guys see me always in a sad mood, I am actually pushing a nerve here to relieve the pain," and touched the right side of his face.

The health issues have not affected Dueterte's work, however, said presidential spokesman Ernesto Abella. "Nothing serious," he told reporters, when asked to comment on Duterte's remarks.

But Duterte missed some events during meetings of the ASEAN grouping of South East Asian nations in Laos in September and last month's Asia-Pacific Economic Cooperation summit in Peru, due to migraine attacks and a bad stomach.

Duterte on Tuesday announced the distribution of 2 billion pesos ($40 million) worth of medicines to poor families plagued by illness, and to drug dependent individuals at rehabilitation centers.

He told drug users to stay indoors or face arrest.