Russia said Thursday it was stepping up field training for tank, artillery and infantry units in three regions next to the Ukrainian border in a powerful display of military might.The move came as thousands of paratroopers also began exercises close to Ukraine on Thursday, while Russian gunmen patrol Crimea ahead of a referendum on it joining Russia on Sunday.

The armed forces are “increasing the intensity of field training exercises,” the defense ministry said in a statement, saying the exercises were being carried out in the Rostov, Belgorod and Kursk regions bordering Ukraine, as well as one non-border region.“The main aim … is a multi-faceted check of the units’ cohesiveness followed by the performance of battle training assignments in unfamiliar terrain and untested firing ranges,” the ministry said.

It said the exercises would continue until the end of March but did not specify how many troops were involved.Deputy Defence Minister Anatoly Antonov said Wednesday Moscow had permitted a request for a Ukrainian reconnaissance plane to carry out an observation flight over the border region.