This is what happened in Russia and in the naval shock in Ukraine

The long crisis between Ukraine and Russia saw a dangerous escalation on Sunday, as the Russian coastguard attacked and seized three Ukrainian army ships and their crew. The Ukrainian government declared martial law on Monday in response to the attack, which gave rise to public demonstrations and international condemnations of Russia.

Naval confrontation is one of the most important events in Ukraine and in Russia's hostilities since the annexation of Crimea by Russia in 2014, which could lead to further conflict if tensions are not controlled.

Here's what you need to know about the incident and its aftermath:

Russia and Ukraine have different versions of events, and each blames the other for being the instigator of the incident. But at the center of the clashes are three Ukrainian military ships that was attacked Russian coastguards as he headed for the Ukrainian port city of Mariupol.

The only way for Ukrainian ships to go to Mariupol was to cross the Kerch Strait, a narrow waterway connecting Russia and Crimea to the Sea of ​​Azov. Ukraine and Russia signed a treaty In 2003, both countries have full access to the Sea of ​​Azov and the Kerch Strait, but Russian Coast Guard ships decided Sunday to prevent Ukrainian ships from crossing the Strait. A Russian ship struck a Ukrainian military tug before Coast Guard vessels opened fire on the two Ukrainian combat ships it was escorting.

A video taken aboard the Ukrainian tug captured the beginning of the attack:

The three Ukrainian ships were badly damaged and six of their crew were injured, according to the Ukrainian military, who said that Russia then seized the ships and arrested 23 Ukrainian crew members. Russia, however, claims that only three Ukrainians were slightly injured and accused Ukraine and "its Western bosses" of having provoked the attack as "pretext for strengthening the sanctions" against the Kremlin. The two countries also disagree on whether Ukraine has informed Russia in advance of the passage of ships in the strait. Moscow denied Kiev's statement that its army had alerted Russian forces several times of its intentions.

It is unclear what will happen to the Ukrainian crew members that Russia holds in captivity. The status of damaged ships is unknown and it is not clear whether Russia will take further steps to block access to the Azov Sea.

Tensions on both the Kerch Strait and the access to the Sea of ​​Azov have been building since Russia annexed Crimea, a seizure that de facto gave the Kremlin military control of the Strait. About half of the Ukrainian coastline lies on the sea of ​​Azov, and many of its shipping routes cross the strait, which means that Russia has power over a critical bottleneck.

Over the past year, the dispute over access to the sea has intensified. Ukraine and Russia have each accused each other of military accumulation and illegal activities in the region. Kiev claimed that the Russians were preventing ships from crossing the strait. Ukraine has also condemned the opening of a multi-billion dollar bridge in May, it crosses the strait to connect Russia and Crimea. Last month, Ukraine announced that it build a new military base on the sea of ​​Azov to counter the Russian presence.

The increasingly difficult situation around the sea has developed in parallel with the ongoing conflict in eastern Ukraine, where the fighting of recent years between separatists backed by Russia and the Ukrainian army have killed more than 10,000 people. Russia has denied any direct involvement in this conflict – but one of the things that makes the Sunday incident so remarkable is that the Kremlin has done nothing to hide its hostile acts.

A number of major questions arise as to the origin of the crisis and whether the international community can defuse the situation. The United Nations Security Council has held a emergency meeting on monday to discuss the incident, while a number of Western countries and NATO officials have criticized Russia for aggression and violation of international law.

The Ukrainian government has declared a 30-day martial law, which would give authorities the power to limit freedoms in the country. The Ukrainian parliament approved the measures late Monday, after President Petro Poroshenko called on lawmakers to support this initiative. This is the first time that Ukraine has imposed martial law since the start of its conflict with Russia in 2014, and this could have major domestic implications.

Some critics of Poroshenko allege that the measures are a political ploy strengthen support for his presidency. His approval ratings have fallen in recent months and he is likely to be removed from office in the country's presidential election in March. Declaring martial law could potentially allow Poroshenko to postpone the vote and rally more support through anti-Kremlin appeals.

After clashes in the Navy on Sunday, hundreds of protesters gathered in front of the Russian Embassy in Kiev to protest. An embassy car was burned. Protesters from the far right also gathered in front of the Ukrainian parliament on Monday to demand vigorous action against Russia and brandish nationalist banners.

Although US Ambassador to the United Nations, Nikki Haley, criticized Russia and called on the Kremlin to "immediately stop" illegal actions, President Donald Trump was rather unobtrusive about the incident. In a brief statement Monday afternoon, he told reporters: "We do not like what's going on, anyway, we do not like what's going on and hope everything will be sorted out. "