Ukrainian President Petro Poroshenko said the measure would prevent Russia forming ‘private armies’ in Ukraine.

Ukraine has banned Russian men aged between 16 and 60 from entering the country for the duration of martial law after Russia seized three Ukrainian ships and 24 sailors.

The measure was announced on Friday at a security meeting where Ukraine’s President Petro Poroshenko assured that the move would “prevent the Russian Federation from forming detachments of private armies” in Ukraine “similar to the operations they tried to carry out in 2014.”

Ukraine believes that Russian citizens, including Russia’s regular soldiers, are fighting alongside Moscow-backed rebels who in 2014 seized parts of Ukraine’s Donetsk and Luhansk regions, declaring them independent from Kiev.

Peter Tsigikal, the head of the state border service of Ukraine, told the president that his department was on the highest level of combat readiness, security measures were boosted on the border with Russia and the Russian-annexed Crimean peninsula.

“The male citizens of the Russian Federation aged 16 to 60 are not allowed in. As for the citizens of Ukraine, there are no restrictions,” Tsigikal said.

The travel restriction on Russian men would not apply in cases where they visit for “a funeral or some other humanitarian purpose”, he said.

Andriy Demchenko, Ukraine’s border service spokesman, reiterated that it was not a blanket ban.

“Russian citizens will go through an additional interview at the border, their previous visits to Ukraine will be scrutinised,” he told Al Jazeera.

“The decision on each case will be made at the point of entry following the strengthened border control. The exceptions might be applied to individuals with diplomatic status in Ukraine, transport service personnel, people who have temporary or permanent residency in Ukraine, also those who are coming for humanitarian purpose, including death or illness of close relatives.”

Maria Zakharova, Russia’s foreign ministry spokeswoman, said at a news conference in Moscow that her country would not respond in kind as it would be “irrational”.

She also accused Poroshenko of using martial law as a way of “raising his falling electoral rating in an attempt to earn points during the latest Russophobic wave.”

The development came two days after martial law came into force in 10 out of 27 Ukrainian regions for a period of 30 days.

Poroshenko has said the imposition of martial law aimed to prevent an all-out Russian invasion, after Moscow on Sunday blocked the route of three Ukrainian military vessels in shared waters.

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The ships were travelling from the Black Sea to the Sea of Azov through the Kerch Strait when they were intercepted.

The confrontation resulted in the seizure of all three ships by Russia and the capture of 24 Ukrainian crew members who were later put under 60-day pre-trial detention and sent to Moscow.

Poroshenko addressed the issue at the security meeting on Friday, saying: “During each of my telephone conversations [with international partners], we raised the issue of consolidating the common position of the world regarding the demand for Russia to immediately release the military.”

Also on Friday, Ihor Huskov, a senior official at Ukraine’s state security service (SBU), was quoted by Reuters news agency as saying that Kiev was considering “mirror actions”.

“Decisions are being considered with regard to the conduct of appropriate mirror actions as a response to the actions of the aggressor,” he said, without elaborating what those actions could be.

The scenario was not discussed at the meeting between Poroshenko and his security team.

With additional reporting from Kiev by Al Jazeera’s Tamila Varshalomidze