Belarus's border authority has alleged, without producing evidence, that a Ukrainian military helicopter flew up to a kilometer into Belarusian territory, underscoring increasingly tense bilateral relations as Minsk and its ally Moscow test Western resolve in the region.

Ukrainian officials did not immediately comment on the accusation by the Belarusian state border service on December 4, which said the alleged overflight happened during military drills, according to Russian news agency RIA Novosti.

There was no outside confirmation of such a violation.

Belarus is engaged in a bitter diplomatic standoff with the West over Alyaksandr Lukashenka's crackdown on dissent since a disputed election in 2020 and what the European Union has called his 'weaponization' of Middle Eastern migrants to create a crisis on Belarus's border with EU members Latvia, Lithuania, and Poland.

The European Union, United States, and other Western powers this week imposed a fifth round of sanctions on Lukashenka and his elites over alleged rights and other abuses.

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Lukashenka has increasingly relied on the diplomatic, economic, and military support of Moscow, which has recently staged joint military drills and last month launched regular air patrols over Belarus's western border.

Russia has also been accused of a major troop buildup in its west in what Kyiv and Washington have suggested is part of preparations for a possible invasion of Ukraine.

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In July, Lukashenka fully closed Belarus's border with Ukraine after he alleged that the United States and its allies had been plotting a coup to topple him from power, the latest such accusation rejected by Washington or its allies.

Minsk on November 30 reversed policy to recognize Russia's 2014 seizure of Crimea from Ukraine -- a takeover that has been overwhelmingly rejected in the United Nations -- as Kyiv continues to battle Kremlin-backed separatists in eastern Ukraine.

Meanwhile, many of the thousands of Iraqis and other migrants from the Middle East hoping to travel to the West remain camped out in Belarus near the Polish border.

Belarusian sources have said thousands have already been flown back to the Middle East since Turkey and other countries began cooperating more closely to thwart Minsk's alleged efforts to ship in migrants to put pressure on the EU border.

Copyright (c) 2018. RFE/RL, Inc. Republished with the permission of Radio Free Europe/Radio Liberty, Washington DC 20036