
Ukraine has started calling up its military reserves for training amid fears Russia is poised for an invasion.

President Petro Poroshenko is fearful that Putin could try to seize the ports of Mariupol and Berdyansk, located around the Sea of Azov.

The aim would be to create a land corridor between the eastern Ukrainian regions of Donetsk and Luhansk, which are partly controlled by Russian-backed separatists, and Crimea, which has been annexed by Moscow.

But Kremlin spokesman Dmitry Peskov dismissed the rumours as 'absurd' and described them as 'another attempt to generate tension'.

Ukrainian servicemen take part in a military exercise on the firing range near of Gncharivske village, about 120 km from capital Kiev

Russia has sharply increased the number of its troops along the border with Ukraine and in Russian-occupied Crimea. Pictured: Ukrainian soldiers conduct drills

Preparing for war: Ukrainian servicemen take part in a military exercise on the firing range around 75 miles from Kiev

Military exercises are held in the areas where martial law is in effect. First-line reservists were also called into training

For the duration of martial law, Ukrainian authorities barred entry to all Russian men aged 16 to 60 in a move the Ukrainian leader said was needed to prevent Russia from further destabilizing the country

Ukraine has begun calling up its army reserves for training as part of 30 days of martial law amid fears Russia could invade

Soldiers took part in military drills intended as a show of force to Russia around 75 miles north of Kiev on Monday

Ukrainian strategists are worried that Russia will attack the ports of Mariupol and Berdyansk, along the Sea of Azov, in an attempt to make a land corridor between eastern Ukraine and Crimea

Tanks take part in live-fire drills in Ukraine on Monday. Russia has denied any rumours of an invasion, saying they are 'absurd' and are designed to stoke up tensions

Ukrainian President Petro Poroshenko spoke to soldiers north of Kiev after declaring martial law across much of the country

Ukrainian officials raid Russian churches Ukrainian authorities on Monday raided three Orthodox churches aligned to Russia as political and religious tensions between the two countries grow. Police and security services also searched the homes of priests who have declared their allegiance to the Russian branch of the Orthodox church. The Ukrainian Orthodox Church was recently granted independence from Moscow in a controversial ruling that prompted cheers from Kiev but anger in Moscow. The raids on the churches in northern Ukraine were part of a probe into the possible violation of a law on equality of religious belief. No-one was arrested. Advertisement

It comes after the Russian coast guard fired upon and seized three Ukrainian naval vessels and their crews off the Crimean Peninsula in the Kerch Strait.

The speaker of Russia's lower house of parliament announced on Monday that he plans to give medals to the sailors who fired upon then seized the Ukrainian boats.

Vyacheslav Volodin said they acted 'faultlessly and courageously' to thwart a violation of its maritime border.

Poroshenko has also responded to the fracas by introducing martial law for 30 days in much of Ukraine, but is now considering further action.

For the duration of martial law, Ukrainian authorities barred entry to all Russian men aged 16 to 60 in a move the Ukrainian leader said was needed to prevent Russia from further destabilizing the country.

Poroshenko said Monday that some reservists will be summoned for training as part of martial law.

He also said that some military units will be redeployed to strengthen the nation's defenses.

'Ukraine is taking its own steps in response to the threat of a large-scale Russian invasion,' the Ukrainian leader said.

Over the weekend, Poroshenko said that Russia has deployed a large number of troops and tanks along its border and intends to push inland.

A helicopter lands at a compound of the Ukrainian Ground Forces training center to the north of Kiev on Monday

Ukraine has been on edge since Russia fired upon and then seized three of its military vessels in the Sea of Azov

Russia and Ukraine have been waging a conflict-by-proxy in the Donbass and Luhansk regions since Putin ally Viktor Yanukovych was kicked out of power in 2014

Ukrainian soldiers move to position in a APC during military drills in base Honcharivske, Chernihiv region

A Ukrainian guard stands close to the border with Russia after it was closed to all Russian males aged 16 to 60

Ukraine also accused Russia of blockading its ports on the Sea of Azov.

Peskov rejected Kiev's claim that Russia was blocking traffic to and from Ukrainian ports on the Sea of Azov, saying that navigation has continued normally except for occasional breaks because of bad weather.

The separatist conflict in eastern regions forming Ukraine's industrial heartland has taken a toll on the national economy, reducing the cargo flow through the Ukrainian ports of Mariupol and Berdyansk on the Sea of Azov.

The naval incident further stoked tensions. Vitaliy Sinhur, a dock worker in Berdyansk, said the movement of ships has significantly ebbed.

Over the weekend, Poroshenko urged Germany and other Western allies to boost their naval presence in the Black Sea to help deter Russia from further aggression.

Ukraine's deputy defense minister, Anatoliy Petrenko, said the country is talking to its Western partners to respond to Russia's 'escalatory actions.'

Amid the tensions, the Russian military said its forces in Crimea were conducting drills involving Bal and Bastion long-range anti-ship missile systems.

In the Nov. 25 incident, three Ukrainian naval vessels were heading from the Black Sea into the Sea of Azov when they were blocked by the Russian coast guard near the Kerch Strait between Russia's mainland and Crimea.

A Ukrainian solider is pictured during military drills north of Kiev amid fears that Russia could attack soon

Armoured personnel carriers work their way across snowy terrain between artillery pieces during drills in Ukraine

Ukrainian servicemen take part in brigade tactical exercises with combat shooting near Goncharivske village

Tensions have flared since Russia rammed, shot at and seized three Ukrainian ships near the Kerch Strait (pictured), which it temporarily closed

Two Ukrainian ships seized by Russia are seen in the port of Mariupol. Russia also captured 24 Ukrainian sailors

After many tense hours of maneuvering, the Russians opened fire and seized the Ukrainian vessels and 24 crew members.

The Ukrainian seamen have been put in custody for two months pending Russia's investigation into the clash.

Ukraine and Russia have traded blame for the naval incident that further escalated the tug-of-war that began in 2014 when Russian annexed Crimea and backed separatist rebels in eastern Ukraine.

Ukraine says that its ships were operating in line with a 2003 treaty with Russia envisaging free navigation for vessels of both countries in the Sea of Azov and the Kerch Strait.

Russia is adamant that the Ukrainian ships had entered its waters without permission.

Later this week, the Ukrainian parliament is expected to mull a presidential decree blocking the extension of a friendship treaty, a long-anticipated symbolic move.

Poroshenko has said he tried to arrange a phone call with Putin to discuss the standoff but faced the Kremlin's refusal.

Peskov said Monday that 'no such conversation is planned.'