Briefing the Security Council, in the wake of Sunday's confrontation between vessels from the two neighboring countries off the coast of Crimea, DiCarlo urged them "to refrain from any ratcheting up of actions or rhetoric".
An "immediate de-escalation" of tensions is needed in the Sea of Azov and the Black Sea, she said, underlining the importance of "earnest attempts" to find a peaceful resolution to years of simmering conflict between Russia and Ukraine, Xinhua news agency reported.
"(We) remind both (Russia and Ukraine) of the need to contain this incident so as to prevent a serious escalation that may have unforeseen consequences," she said.
DiCarlo also recalled her previous calls on all parties to avoid any unilateral steps that could deepen the divide or depart from of the spirit and letter of the Minsk Agreements, which set out the necessary steps to restore peace in the eastern regions of Ukraine.
DiCarlo noted that the UN fully supports regional efforts to find a peaceful settlement, and that "renewed and constructive action" was needed by all concerned to overcome the apparent impasse in diplomatic negotiations, she added.
The Security Council meeting followed a procedural vote rejecting the agenda of the day's first meeting on the issue, requested by Russia, which argued that its borders at sea had been violated by Ukraine.
Dmitry A. Polyanskiy, the first deputy permanent representative of Russia to the UN, argued that Ukrainian naval vessels had "illegally" crossed into Russian territory and did not acknowledge efforts made by Russian ships to warn them off.
Such actions were in violation of the UN Charter and norms of international law, he said.
He said responsibility was "borne by those people" who gave the Ukrainian crew "the illegal command". Polyanskiy told Security Council members that the Ukrainian ships were being held in Russian ports, pending an investigation.
In a second meeting the same day, Volodymyr Yelchenko, the permanent representative of Ukraine to the UN, informed the Security Council of his country's account of events, stating that what the Russian representative spoke earlier was an "outright lie".
Six Ukrainian military sailors were wounded in the attack and two of them were in serious condition, the Ukrainian Navy said.
Russia's Federal Security Service (FSB) said that three Ukrainian ships -- Berdyansk, Nikopol and Yany Kapu -- breached the Russian border and conducted dangerous maneuvers in spite of orders of the accompanying vessels from the FSB and Russia's Black Sea Fleet.
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