Behind this week's confrontation between Russia and Ukraine stand two men -– Vladimir Putin in Moscow and Petro Poroshenko in Kiev -– both anxious to shore up support at home.

As much as disputed waters and national pride, it is domestic politics that are driving the worst tensions in years between the ex-Soviet neighbours, experts say.

As the crisis over Russia's seizure of three Ukranian naval ships off the coast of Crimea rumbles on, the two presidents are likely to benefit.

Paper boats left in protest outside the Russian Embassy in Kiev Sergei SUPINSKY, AFP

In Moscow, Putin has seen his usual sky-high approval ratings fall as economic problems continue to bite and after the government pushed through a deeply unpopular pension reform.

"Switching attention to this conflict is in the interests of the authorities," said Konstantin Kalachev, head of the Moscow-based Political Expert Group think-tank.

"Assessments of all levels of government, including the president, have been falling. And here comes the easiest way to protect their ratings."

Despite some economic reforms and growth, Russia has yet to recover from a 2015-16 recession that hit the country hard. Economic sanctions over Ukraine and low oil prices have not helped.

Russian President Vladimir Putin is promising four percent economic growth and a 50 percent reduction in the poverty rate by 2024 BULENT KILIC, AFP

Putin has promised four percent growth and to cut the poverty rate in half by 2024, but the World Bank is forecasting growth of less than two percent over the next two years.

The pension reforms, signed by Putin in early October, sparked rare protests and widespread public opposition.

The reform -- which will gradually increase the retirement age for men to 65 from 60 and for women from 55 to 60 -- was blamed for poor showings by several Kremlin-backed candidates in regional elections.

- Distracting attention -

Putin was re-elected to a fourth term in March with nearly 77 percent of the vote but recent polls have seen his support crumbling.

Only 40 percent of respondents in a Levada Centre survey last month said they would now vote for Putin, and 61 percent said they held him personally responsible for the country's problems.

A fresh conflict with Ukraine, and the nationalist fervour it stirs up, is likely to give those numbers a boost, Kalachev said.

"If you look at the discussion on social networks, it's already working," he said. "Again we're seeing the 'hurrah-patriotic' sentiments, the Ukrainophobia. Talk of a possible war is a great way to distract attention."

Ukrainian President Petro Poroshenko is struggling to hit even 10 percent support, according to recent surveys Genya SAVILOV, AFP

In Kiev, Poroshenko is also facing difficult poll numbers -- dismal ones, in fact -- as he prepares to make a bid for re-election in March.

Elected in May 2014 with more than 50 percent of the vote, Poroshenko now trails in third or fourth place in voting intentions.

Recent surveys had him struggling to hit 10 percent support, against 20 percent for his main rival, the ex-premier Yulia Tymoshenko.

Poroshenko was forced recently to apologise for failing to meet his 2014 election promise to bring the separatist regions of eastern Ukraine back under central control.

He also faces harsh criticism over persistent corruption and a major economic crisis that has seen austerity measures imposed in exchange for Western aid.

- 'Defender of Ukraine' -

Standing up to Russia over the Ukrainian ships is sure to shift the spotlight onto Poroshenko's role as commander-in-chief, Ukrainian political analyst Oleksander Medvedev said.

Poroshenko will now be seen as "the big boss, who everyone listens to and talks about," Medvedev said. "Everything else, including criticism of the economic situation, will move into the background."

By winning parliamentary approval for his plan to impose martial law on border regions, Poroshenko has already scored one political victory, even though he had to reduce its duration from 60 days to 30.

A source close to the president told the RBC-Ukraine news agency that the martial law plan aimed to "strengthen Poroshenko's image as the defender of Ukraine" and to "redirect the campaign" onto issues of national security.

In an editorial on Tuesday, Moscow's Nezavisimaya Gazeta said both sides had clear political motives in keeping the crisis going.

"Who benefits from an escalation of conflict between Moscow and Kiev? In an atmosphere of tension, it is easier for any politician to keep power.... This is well understood in Moscow and in Kiev," it wrote.

"Kiev and Moscow have learned how to live with conflict, and how to use it."