President Petro Poroshenko instructed his government on Thursday to consider temporarily closing Ukraine's porous border with Russia to help halt its "intervention" in the Westward-leaning former Soviet state's affairs.
A decree published on the presidential website ordered the government "to settle... the issue of temporarily closing checkpoints on Ukraine's state border with the Russian Federation to cars, sea and pedestrian traffic."
It adds that the 2,000-kilometre (1,200-mile) land frontier with Ukraine's giant northeastern neighbour may be closed "to other forms of traffic" if necessary.
The decree said it was issued "in connection with the continued intervention of the Russian Federation in Ukraine's internal affairs."
Both Kiev and its Western allies accuse Russia of sending elite forces and heavy weapons such as surface-to-air missiles into eastern Ukraine to help the separatist uprising that pro-Kremlin gunmen launched in April.
Russia flatly denies the charges and dismisses NATO satellite imagery purporting to show its troops in Ukraine as fabrications designed to back the military bloc's expansion toward its boarder.
A senior security source told AFP the instructions were originally drafted by Ukraine's National Security and Defence Council at the end of August in order to limit future cross-border travel to rail service and passenger flights.
The source said that such traffic "would be substantially easier to control".
A spokesman for Ukraine's state border service said no additional security measures had yet been taken and that cars were still allowed to pass along the dozens of border crossing linking the two countries.
Ukraine "has closed checkpoints that have long been under attack from the rebels and the Russian side of the border," spokesman Andriy Kucherov said by telephone.
"The rest of the Ukrainian-Russian border is operating as before."