Duterte said last week one of the top priorities of his trip to Russia was to secure precision-guided bombs to use on Islamic militants in the southern Philippines.
He had also previously said he hoped the Philippines would soon be able to start acquiring other Russian weapons.
The Philippines and Russia established diplomatic ties 41 years ago but until Duterte took office relations remained relatively low-key.
This was partly due to Manila’s alliance with the United States.
Philippine-Russian trade last year totalled just $226 million, according to government data, while Philippine-US trade was worth more than $18 billion last year.
Duterte’s visit to Moscow will be a “propaganda victory for Putin and a soft-power coup for Russia”, analyst Richard Javad Heydarian told AFP.
“It will be their way of poking the eye of America.”
China sidesteps Duterte claim of war threat over sea row
China on Monday sidestepped claims by Philippine President Rodrigo Duterte that it had threatened to go to war over the disputed South China Sea.
Duterte, who met with Chinese President Xi Jinping and Premier Li Keqiang in Beijing last week, said Friday the leaders had raised conflict as an option to resolving their competing claims to the waters.
“I really said it to their face. That is ours and we intend to drill oil there,” said Duterte, who claimed he made the comments public in response to domestic criticism he was being too weak with China over the row.
“And they told me: ‘Well, we’re friends. We do not want to quarrel with you. We want to maintain the present warm relationship. But if you force the issue we’ll go to war.'”
China’s government on Monday did not directly comment on Duterte’s version of the leaders’ conversation, but said it would “work with the Philippines to peacefully resolve disputes through friendly consultation”.
China sought to “deepen cooperation in other fields so bilateral relations can move forward in a sound steady way and also contribute to regional peace stability,” foreign ministry spokeswoman Hua Chunying told reporters.
The rival claims to the South China Sea, which is believed to sit atop vast oil and gas deposits, have for decades made it one of Asia’s potential military flashpoints.
China claims most of the sea, a key waterway for global shipping, and has reclaimed disputed reefs and installed military facilities on them.
Malaysia, Brunei, Vietnam and Taiwan also have overlapping claims.
An international tribunal ruled in July last year that China’s claims to most of the sea were without legal basis, in a case filed by the Philippines under Duterte’s predecessor, Benigno Aquino.
But China vowed to ignore the ruling and warned the Philippines against trying to use the verdict as leverage.
Duterte, who began his six-year term in June last year, agreed to take a soft stance with China, claiming that if he did it might lead to war.
Duterte has also sought closer ties with China to win billions of dollars of Chinese investments and loans, while loosening the Philippines’ long-standing alliance with the United States.