Ukrainian President Petro Poroshenko is due to take part in talks with his Russian counterpart, Vladimir Putin, at a summit in Minsk, capital of Belarus.
The meeting comes amid rising tension between the two countries over Ukraine's military campaign against pro-Russian separatists.
Ukraine said that its troops had captured 10 Russian servicemen in eastern Ukraine.
Russia has repeatedly denied supporting the rebels.
More than 2,000 people have died in months of fighting between Ukrainian forces and separatists in Donetsk and Luhansk regions.