Russia has seized three Ukrainian naval vessels off the coast of the Crimean Peninsula in a major escalation of tensions leading Kiev to announce early on Monday that it will impose martial law. Ukrainian President Petro Poroshenko tweeted he will propose to the Supreme Rada (parliament) to approve the imposition of martial law following the seizure on Sunday by the Russian coastguard forces in the Black Sea, Efe news reported. Poroshenko said that as president and commander-in-chief of the armed forces and in accordance with the Constitution, he has decided to support the proposal of the Military Committee of the National Security and Defence Council (NSDC). The Ukranian leader said he hoped the Rada would quickly approve his proposal. However, he added the state of emergency would not necessarily include the mobilisation of the Army, but added that "you have to be prepared". He also said that martial law does not mean the introduction of restrictions on the rights and fundamental freedoms of citizens. The Secretary of the NSDC, Oleksandr Turchynov, proposed that the martial law be in force for 60 days in order to create the conditions to repel a possible "military aggression" and any threat to the independence and territorial integrity. He said that they were talking about the danger of a provocation not only in the Black and Azov seas, but also on land, and that they see the intense preparations of the Russian military units that are close to the northern, eastern and southern borders of the Ukraine. He recalled that this was the first time that Russia has openly attacked Ukraine, since, until now, it had done so "secretly" through hybrid warfare methods. For his part, the Ukrainian Foreign Minister, Pavlo Klimkin, described the seizure of the Ukrainian ships, during which six soldiers were wounded, as an "act of aggression." He added that now they have an aggression on Ukrainian territory and also a war with Russia in neutral waters. The Federal Security Service (FSB, former KGB) of Russia confirmed around midnight after Sunday that the seizure on Sunday afternoon of two small Ukrainian Navy vessels and a tugboat in Russian territorial waters took place after they supposedly performed "dangerous maneuvers", something that Kiev denies. The Ukraine maintains that its vessels were seized in neutral waters when they returned to the port of Odessa in the Black Sea from which they had departed on Sunday morning. The FSB also admitted to opening fire on the Ukrainian ships to force them to stop, adding that their coastguards attended to the injured Ukrainian crew and that "their lives are not in danger." Ukraine had already earlier accused a Russian coast guard ship of ramming one of its tugs on Sunday, as it circumnavigated the Crimean peninsula. Despite Russian warnings, the Ukrainian fleet continued its course to the Sea of Azov, which is why the port authorities closed the Kerch Strait. Russia accuses Ukraine of trying to provoke a situation of conflict in the region, while the Ukrainian Foreign Ministry called on the international community to condemn the Russian aggression. Tension in the Sea of Azov skyrocketed since Moscow inaugurated the Crimean Bridge linking the peninsula with Russia in May, after which inspections of Ukrainian vessels intensified, which Kiev considers a de facto blockade of its ports in the Sea of Azov.