President Rodrigo Duterte is set to visit Russia for the second time in October.

Presidential Spokesperson Salvador Panelo told reporters on Wednesday Duterte accepted the invitation by Russian President Vladimir Putin to visit Moscow again.

"He (Duterte) said he was invited by the Russian President and he accepted it. He'll just announce what will happen there," he said.

He said the foreign trip could likely take place by the first week of October.

Panelo, also the chief presidential legal counsel, said the coming trip could mean "further improved relations between the two countries."

Duterte first went to Russia in May 2017.

But shortly after he arrived in Moscow, he returned immediately to the Philippines due to the attack of the Maute-ISIS terrorist group in Marawi City on May 23, 2017.

While in Russia, Duterte declared martial law in the entire Mindanao.

The Marawi siege lasted for five months until October 2017. But up to now, southern Philippines has remained under martial rule due to rebellion.

Martial law in Mindanao is set to expire by the end of this year unless Duterte would again ask Congress for another extension and this be granted. Celerina Monte/DMS