According to The Associated Press, NATO has announced it has suspended meetings with Russia and is putting its cooperation with the nation under review.
NATO Secretary General Anders Fogh Rasmussen tweeted on his own account:
Reuters also reports the alliance is planning to increase its engagement with Ukraine's leadership.
Earlier Wednesday, armed men forced U.N. envoy Robert Serry was to seek shelter in a cafe, reportedly to chants of, "Russia! Russia!" Serry then agreed to abandon his mission to end the stand-off.
More from AP:
PARIS (AP) — The head of NATO says it is responding to Russia's military intervention in Ukraine by suspending most of the military alliance's meetings with Russia and reviewing all of its cooperation with Moscow.
NATO Secretary-General Anders Fogh Rasmussen said Wednesday that ambassadors for NATO's 28 member states decided after a meeting with their Russian counterpart to suspend plans for a joint mission as well as all civilian and military meetings.
Rasmussen said because of Russia's military action in Ukraine's Crimean peninsula "the entire range of NATO-Russia cooperation (is) under review."
Rasmussen said the alliance will continue to meet with Moscow at the political level but insisted that halting all other cooperation "sends a very clear message to Russia."
He also said NATO decided "to intensify our partnership with Ukraine."