Observers from the Organisation for Security and Co-operation in Europe were set to begin arriving Tuesday in southern Russia on their mission to monitor two border crossings with rebel-held Ukraine, the OSCE said Tuesday.

The first members of the team of 16 civilian monitors were due to arrive in Russia's southern Rostov region where they were expected to hold meetings with officials from the regional administration, border guards and customs service, said OSCE spokeswoman Tatyana Baeva.

They could begin visiting the Russian border posts known as Donetsk and Gukovo which they will be monitoring as soon as Wednesday, she said.

Russia has been keen to refute Western allegations that it has been supplying weapons across the border to pro-Russian rebels.

However the OSCE decision last week to deploy the monitors on the three-month mission tasked them with monitoring the situation at the border crossings, and not the entire border.

"The monitors were sent where the border isn't being crossed," independent Russian defence analyst Pavel Felgenhauer told AFP.

"There is no use for such monitoring as it is summer and it is dry, so you don't need roads and can cross the border at any place," he added.

Russian Foreign Minister Sergei Lavrov said Monday that the OSCE observers were free to use drones or satellites to monitor the border.

But OSCE said that a tender it held last week for drones was for its monitoring mission in Ukraine rather than its border mission.

"The OSCE Observer Mission that is currently heading to the Russian Federation does not plan on using the services of the drones," said Baeva.