Ukraine's ambassador to the United Nations asked an emergency session of the Security Council on Saturday “to do everything possible now” to stop Russian “aggression” as Russian troops took over the strategic Crimea region.

U.N. Secretary-General Ban Ki-moon urged Russian President Vladimir Putin in a phone call to “urgently engage in direct dialogue with the authorities” in Kiev.

Calling the situation in Ukraine “as dangerous as it is destabilizing,” U.S. Ambassador to the U.N. Samantha Power told the council, “It is time for the Russian military intervention in Ukraine to end.”

Power and other members of the council called for sending international monitors to Ukraine as soon as possible to observe the situation, and Power warned that “Russia's provocative actions could easily push the situation beyond the breaking point.” She also mentioned work on an international mediation mission to send to Ukraine.

The Security Council met in emergency session for the second straight day on the rapidly developing events in Ukraine. It met briefly in an open, televised session, despite initial objections from Russia, then resumed meeting behind closed doors.

The council took no action. As a permanent member of the council, Russia has veto power and can block the U.N.'s most powerful body from adopting any resolution criticizing or sanctioning Moscow.

But the current council president, Luxembourg Ambassador Sylvie Lucas, said members stressed the importance of Ukraine's territorial integrity and the need to lower tensions, in addition to the need for international monitors.

Russia's U.N. ambassador, Vitaly Churkin, said the new government in Kiev needs to get away from “radicals” and warned, “such actions they're taking could lead to very difficult developments, which the Russian Federation is trying to avoid.”

Russia has given refuge to Ukraine's now-fugitive president, Viktor Yanukovych, who fled after demonstrations turned violent amid tensions over his decision to turn Ukraine toward Russia, its longtime patron, instead of the European Union.

Churkin said Russia was intervening at the request of pro-Russian authorities in the semi-autonomous Crimea, which is largely Russian-speaking and is home to Russia's Black Sea navy fleet.

British Ambassador Mark Lyall Grant, who called for Saturday's meeting, told reporters after the meeting that `there is no justification for Russia's military activities in the last 48 hours.”

Deputy Secretary-General Jan Eliasson called the situation in Ukraine “very difficult and very dangerous” and said they were seeing “negative signs, serious signs, risks of escalation.”

Ukraine's U.N. ambassador, Yuriy Sergeyev, asked the other four permanent Security Council members _ the U.S., Britain, France and China _ for help in stopping Russia's “aggression.”

Sergeyev also said Russia rejected Ukraine's proposal to hold immediate bilateral consultations.

When asked later whether Ukraine is at war with Russia, Sergeyev said, “No. We are not at war. We are trying to avoid any clashes. We are being provoked.”

Ban said earlier Saturday that he is “gravely concerned about the deterioration of the situation” in Ukraine. He called for “full respect for and preservation of the independence, sovereignty and territorial integrity of Ukraine.”

Ban later spoke by telephone with Putin, and a statement from Ban's office said, “It is crucial to restore calm and proceed to an immediate de-escalation of the situation.”

“Cool heads must prevail and dialogue must be the only tool in ending this crisis,” Ban said..

Ban planned to meet Sunday in Geneva with his special envoy Robert Serry, the Netherlands' first ambassador to Ukraine.

Ban on Friday asked Serry to go to Crimea as part of a fact-finding mission.  However, after consulting with authorities in the region, Serry decided that a visit to Crimea was not possible and headed to Geneva. (AP)