Russian Federation claimed the ships it seized violated its territorial waters, but the strait is considered shared under a 2003 agreement.
Ukraine's leader has called on Germany and its allies to boost their naval presence in the Black Sea to deter Russian Federation from further aggression in the region.
Russian President Vladimir Putin has said that the incident was a provocation prepared in advance as a pretext to introduce martial law in Ukraine ahead of the country's presidential election.
The martial law order included a ban on entry to Ukraine of all Russian males aged 16 to 60, a move Poroshenko said is created to prevent undercover Russian military units from infiltrating the country.
Ukrainian TV channel "112 Ukraine" on Saturday showed Poroshenko presenting new and overhauled military aircraft, helicopters and drones to the Ukrainian army.
Over the weekend, Poroshenko said that Russian Federation has deployed a large number of troops along its border with Ukraine and alleged that the Kremlin intends to push inland into Ukraine.Ukraine also accused Russian Federation of blockading its ports on the Sea of Azov. He also said that some military units will be redeployed to strengthen the nation's defences.
Russia is resisting worldwide calls to release three Ukrainian naval ships that its border patrols fired on and seized in the strait near Russian-annexed Crimea last weekend.
Ukraine's deputy defense minister, Anatoliy Petrenko, said the country is talking to its Western partners to respond to Russia's "escalatory actions".
Russian Federation must release the Ukrainian sailors and ships, Stoltenberg said.
Putin noted that Russian Federation had presented the chronology of the incident to foreign leaders, and "it is hard to object to it".
Last weekend, Russian Federation seized three Ukrainian naval vessels and their crews in the narrow strait that separates the Black Sea from the Sea of Azov.
Germany and France have been trying to mediate the dispute.
After many tense hours of maneuvering, the Russians opened fire and seized the Ukrainian vessels and 24 crew members.
German Chancellor Angela Merkel says Russia must allow ships access to Ukrainian ports on the Sea of Azov through the Kerch Strait, which separates the Russian mainland from the annexed Crimean Peninsula. The Ukrainian vessels were arrested by Russian Federation after failing to respond to a demand to stop.
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.
Putin, also speaking in Buenos Aires, said he told foreign leaders "how the situation unfolded" and then accused Ukraine's government of stoking the conflict "to cover up one's failures in economic and social policy".