Russian news agencies reported on August 4 that more than 400 Ukrainian soldiers crossed into Russia overnight, allegedly to avoid fighting with pro-Russian rebels in eastern Ukraine.
The Ukrainian military confirmed that an undisclosed number of troops had crossed into Russia, but it denied Russian media reports the soldiers were seeking refugee status.
Vasily Malayev, a senior Federal Security Service (FSB) official, told Russian news agencies that a "humanitarian corridor was opened" for 438 Ukrainian soldiers who asked permission to enter Russia.
The soldiers were reportedly surrounded by the rebels after they ran out of ammunition.
Malayev later said 180 of the troops had requested to be returned to Ukraine.
Meanwhile, officials in Kyiv said on August 4 Ukrainian forces recaptured the eastern town of Yasynuvata, an important railway hub north of Donetsk.
They say five soldiers were killed and 15 others wounded in clashes in the past 24 hours.