VIENNA (AP) — The Organization for Security and Cooperation in Europe is sending a new team to observe military developments in tense regions of Ukraine after pro-Russian forces rebuffed previous attempts to monitor Crimea.

The 57-nation organization said Tuesday the new team's mandate has been extended beyond Crimea to eastern Ukraine.

Like Crimea, parts of eastern Ukraine have a large ethnic Russian population. Pro-Russian forces have secured many of Crimea's military installations as the region prepares for a referendum on whether to join Russia. The request from Ukraine for the team to also monitor the east appeared to be prompted by fears of similar developments there.

Pro-Russian units foiled the previous team's attempts to enter Crimea last week, at one point firing warning shots to force the mission to turn back.