WASHINGTON (AP) — Leading members of Congress are demanding that the Organization for Security and Cooperation in Europe immediately deploy international monitors to eastern and southern Ukraine.

A letter sent by Sen. Dick Durbin, an Illinois Democrat, Arizona Republican Sen. John McCain, and six other lawmakers says monitors are needed to defuse tensions in Ukraine after Russia’s takeover of the Crimean peninsula. The lawmakers visited Ukraine last week and say Russia is using “provocateurs and intelligence agents to brazenly stir trouble” in eastern Ukraine as a possible “manipulated pretext for additional military action.”