03/10/2014 08:05 EDT | Updated 05/10/2014 05:59 EDT

CBC's Derek Stoffel forced to stop taking video in Ukraine

A CBC News crew in Ukraine has been stopped from recording video near the northern Crimean border controlled by Russian forces.

The CBC’s Derek Stoffel tweeted Monday: “CBC crew stopped from recording/shooting at northern Crimea border. Pro-Russian defence forces told us to get out of the area now.”

Stoffel and three other CBC journalists were also barred from entering Crimea.

He said they have seen several large Russian military transport trucks in northern Crimea and that it's believed Russia bolstered its force in the region over the weekend. Crimeans are set to vote Sunday in a referendum on whether or not to join Russia.

Several journalists in Crimea have been roughed up or had they equipment taken by armed men.

Last week, the CBC’s Nahlah Ayed reported that shots were fired after a group of unarmed military observers from the Organization for Security and Co-operation in Europe attempted to enter Crimea.

A source told Ayed that “without a doubt” some of the gunmen controlling the border were Russian.