Ukrainian leader warns of the Russian military build-up as he rallies for action after the first open attack by Moscow.

Kiev, Ukraine – More than 80,000 Russian soldiers are present at Ukraine’s borders and the Russian-annexed Crimean Peninsula, as well as the rebel-held regions of Donetsk and Luhansk, according to the Ukrainian president.

Petro Poroshenko‘s remarks on Saturday came six days after a four-year-old conflict between Kiev and Moscow deepened when Russia seized three Ukrainian military vessels and arrested 24 crew members in the Black Sea near the Kerch Strait.

As he rallies for international support against Moscow, Poroshenko said Russia had about 1,400 artillery and rocket systems, 900 tanks, 2,300 armoured combat vehicles, more than 500 military planes and 300 helicopters in and around Ukraine.

Russia has more than 80 Russian military ships and eight submarines in the Black Sea, the Sea of Azov and the Aegean Sea, according to Poroshenko.

Igor Koziy, military expert at the Institute for Euro-Atlantic Cooperation, told Al Jazeera that the numbers Poroshenko gave seemed accurate if the navy and air force figures were added to the ground troops.

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“If you look at the organisational structure of the Russian military, you will see that there are up to 6,000 people in each brigade. They have up to three brigades in Crimea alone.

“There is also navy and air force there. In the south of Russia that borders northern Ukraine, there have built up two whole military bases – three to five brigades each,” he said.

“The possibility of the Russian invasion at the moment is between 70 to 80 percent, especially during the upcoming holiday season. For three to five days, nobody in the world would care about what is going on,” said Koziy.

He also said Moscow was just waiting for an excuse to justify the move.

“[President Vladimir Putin] is still not ready for a very open traditional method because there is no psychological readiness for it inside the Russian army, but it is still on the table.”

‘Russia continues to test the world’

Speaking at an unidentified location where Poroshenko transferred new and repaired fighter jets, helicopters and unmanned areal vehicles to the Ukrainian army, Poroshenko said that “Russia continues to test the world”.

He said that Moscow was trying to see whether it would get away with turning the Azov and Black Seas into a “Russian lake”.

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“This is a tremendous threat, to which we, together with our allies, are looking for a proper political and diplomatic response. But our internal correct answer is to strengthen the Ukrainian army, first of all, the air force,” Poroshenko said.

The Kremlin has accused the president of playing up the conflict with Moscow to secure electoral support in the upcoming presidential poll on March 31 next year.

Olexiy Makeyev, the Ukrainian foreign ministry’s political director, told Al Jazeera that the world should be wary of the Russian militarisation of Crimea, in particular.

“The occupation and subsequent militarisation of Crimea led to the expansion of the area of use of Russian warships and military aircraft in the Black Sea and far beyond, even the Mediterranean basin,” he said.

“Such militarisation has far-reaching consequences for security not only in the Black Sea area but in the whole southern Europe, as well as North Africa and the Middle East.”

Russia condemned

Foreign ministers from the world’s seven biggest economies on Friday condemned Russia’s actions in Kerch Strait as they reaffirmed their “unwavering support for Ukraine’s sovereignty and territorial integrity” at the G20 summit.

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The world leaders stood by Kiev verbally, but German Chancellor Angela Merkel on Thursday called on Poroshenko “to be sensible” and said there was no military solution to the dispute with Moscow.

Merkel also spoke with Putin on Saturday about the conflict.

“We have talked about the situation in Syria and we have talked about the situation in the Sea of Azov, of course, because here any tensions must be avoided,” she told reporters.

She also said access to the Sea of Azov must not be blocked by Russia, which must comply with international law.

Poroshenko initiated martial law in 10 out of 27 regions of Ukraine following Sunday’s confrontation and called on NATO to send military vessels to the Sea of Azov.

Ukraine believes that after seizing Crimea and the eastern regions, Moscow is aiming to monopolise the Azov Sea before coming for the whole of the country.

The conflict in the east of Ukraine has killed more than 10,000 people since 2014.

Follow Tamila Varshalomidze on Twitter: @tamila87v