Ukrainian President Petro Poroshenko signed the law "On the adjacent zone of Ukraine", backed by the Verkhovna Rada, Ukraine's parliament, on 6 December, 2018.
READ MORE: Putin: Kiev's Provocation in Kerch Strait Likely Helped Poroshenko Rise in Polls
The newly-adopted law doubles the zone of Ukraine's control in the Black Sea, and is aimed at the harmonisation of the country's maritime legislation with the legislation of other Black Sea states and other parties to the 1982 UN Convention on the Law of the Sea, the press service added.
Another goal of the law is to prevent smuggling and illegal ship visits to the closed ports of the "temporarily occupied territories of Ukraine".
"Under the law, if a vessel has violated the legislation of Ukraine and is trying to escape, the authorised agency has the right to pursue such a vessel without delay in order to detain and prosecute it in accordance with the UN Convention on the Law of the Sea of 1982. The right to persecution is no longer valid as soon as the vessel that is being pursued enters the territorial sea of the state under the flag of which the ship is sailing or that of any third country", it said.
The move comes nearly a month after a naval incident in the Kerch Strait, which connects the Sea of Azov with the Black Sea, when Russia detained three Ukrainian warships after they violated the Russian maritime border and ignored legal demands to leave the area.
Shortly after that, Poroshenko declared martial law for three months in a number of regions of the country bordering Russia, as well as the coast of the Black Sea and the Sea of Azov.
Russian President Vladimir Putin, for his part, described the incident as a "provocation" used as a pretext to introduce martial law in Ukraine and suggested it could be connected with Poroshenko's low approval ratings ahead of the March 2019 presidential election in Ukraine. On 26 December, Poroshenko announced that he was terminating the period of the martial law.