Moscow and Kiev have been beating war drums ever since Russia seized two Ukrainian Navy ships and a navy tugboat along with 23 crew members on Sunday in the Sea of Azov off Crimea.
The Ukrainian vessels had been trying to enter the Sea of Azov from the Black Sea via the narrow Kerch Strait, which separates Crimea from the Russian mainland. Crimea, on the western shore, is now controlled by Moscow, the eastern shore is Russian territory, and the northern shore is controlled by Ukraine.
Russia and Ukraine blamed each other for the confrontation, with Moscow blaming the three naval vessels of illegally entering its waters and not responding to calls and warning shots from its maritime border patrol boats.
On the other hand, Kiev says the vessels were heading to the Sea of Azov in line with international maritime rules and had informed the Russians about their entry.
Relations between the two countries are still raw following Russia’s 2014 annexation of Crimea from Ukraine in the aftermath of violent clashes between opposition protesters and government security forces that saw the ouster of then-Ukrainian president Viktor Yanukovyc earlier in February the same year.
Another bone of contention between the two sides has been Russia’s backing for a pro-Moscow insurgency in eastern Ukraine.
Another angle of the crisis is the domestic implications in both countries.
Russian Foreign Minister Sergey Lavrov blamed Kiev for what he described as a "provocation," adding that "Ukraine had undoubtedly hoped to get additional benefits from the situation, expecting the US and Europe to blindly take the provocateurs' side."
The stand-off in the Azov Sea is more combustible now than at any time in the past four years as Ukraine has rebuilt its armed forces, previously in disarray, and has a new generation of commanders who are confident and have a point to prove.
Kateryna Kruk, a Ukrainian journalist and political analyst, told TRT World, "Ever since the war has broken out in 2014, Ukraine has seen numerous proofs that Russia is capable of going far and war isn't something the Russian leadership is looking to prevent as they seek to bring Ukraine back into its influence."
"We already have more than 10,000 people killed and millions of internally displaced persons due to the Russian aggressive actions in Ukraine. So Ukraine's position is to avoid any further loss."
Citing thea Russian buildup of military forces along its border, Ukraine imposed martial law, something the country has not done even during the worst of the 2014 fighting in the east.
The number of Russian units deployed along the Ukraine-Russian border has "grown dramatically," while the number of Russian tanks has tripled, Petro Poroshenko said, citing intelligence reports but giving no precise timescale for the buildup.
"After an incident which happened in the Azov Sea we had to ensure that Ukrainian armed forces would be able to repel an attack in case of a full-fledged land invasion. These [Russian] tanks were not withdrawn yet,” the president said in an interview with national television.
"I don't want anyone to think this is fun and games. Ukraine is under threat of full-scale war with Russia," he added.
Poroshenko's critics had also reacted to his call for martial law with suspicion, wondering why the incident merited such a response. Poroshenko's approval ratings have been plunging, and there were concerns that he would postpone a presidential election scheduled for March. The concerns of delay were later addressed when the martial law duration was halved to allow for the elections to be held on time in May 2019.
Russian President Vladimir Putin has also recently seen his high approval rating fall because of unpopular domestic policies.
In the past, successful military action beyond Russia’s borders has buoyed his popularity.
Russia also announced it will add one S-400 anti-aircraft missile system to the three already deployed on the Crimean peninsula.
The mounting Azov Sea crisis will now also feed into this week’s G20 summit, which both Putin and US President Donald Trump are scheduled to attend.
Kruk said, "For Ukraine, the main result of the G20 summit is whether there will be an agreement to introduce new tougher sanctions on Russia and in general what would be the reaction of the world leaders."
"Many Ukrainians fear that the war might enter even the hotter phase and very much know that Russia is capable of it. But the stronger will be the reaction of the West and the more attention to Ukraine, the less likely Russia will do it," she added.
The US president had said he may cancel the long-awaited summit with his Russian counterpart after the confrontation at sea. A Kremlin spokesman said he still expects the meeting between Putin and Trump to go ahead at the G20 summit in Argentina.
Several world leaders, including Turkish President Recep Tayyip Erdogan, have also urged both sides to resolve the issue through dialogue and diplomacy.
Ukraine and Russia must exercise "maximum restraint," UN chief Antonio Guterres said on Tuesday, appealing for a quick reduction in tensions after a naval confrontation sparked the most dangerous crisis in years between the neighbours.
Last week, a senior Russian diplomat accused Western states of deliberately stoking tensions to justify new sanctions.
The European Union will next month consider further sanctions against Russia over the latest flare-up in the Ukraine conflict, the foreign minister of Austria, which holds the rotating EU presidency, said on Tuesday.
But the bloc's top powers Germany and France have so far put emphasis on seeking to calm tensions.