U.N. Secretary General Ban Ki-moon was headed to the region to try to seek a diplomatic way out of the crisis. He was to meet with Russian leaders in Moscow on Thursday, followed by talks Friday with Ukraine's new government.
Ban has repeatedly called for a solution guided by the principles of the U.N. Charter including sovereignty, territorial integrity and unity of Ukraine.
A 34-member U.N. human rights monitoring mission was also scheduled to be in place by Friday. Ivan Simonovic, assistant secretary-general for human rights, expressed particular concern over the security of Tatars and other ethnic minorities in Crimea.
Russian Ambassador Vitaly Churkin dismissed Simonovic's assessment as "one-sided."
Leonard reported from Kiev, Ukraine. Associated Press writers Alexandra Olson at the United Nations and Robert Burns in Washington contributed to this report.