Dozens of heavy Russian military vehicles massed on Friday near the border with Ukraine, where a huge Russian convoy with humanitarian aid came to a halt as Moscow and Kiev struggled to agree on border crossing procedures.
Russia says it is carrying 2,000 tonnes of water, baby food and other aid for people in east Ukraine, where pro-Moscow separatists are fighting government forces.
Kiev and some Western officials have said they believe the convoy could be a cover for a Russian military incursion - a claim Moscow has described as "absurd".
On Thursday, the convoy of some 280 trucks stopped in open fields near the Russian town of Kamensk-Shakhtinsky, about 20 km (12 miles) from the border with Ukraine.
It was still stationed there on Friday morning and a Reuters reporter at the scene saw a dozen armored personnel carriers (APCs) on the move not far from the convoy.
Another Reuters reporter saw two dozen APCs moving near the border with Ukraine on Thursday night.