Authorities in Crimea have declared the republic's independence from Ukraine and formally applied to join the Russian Federation, as Western states have announced sanctions against Russians and others for their roles in destabilizing Ukraine.
The Crimean assembly also declared all Ukrainian state property would be "nationalized."
The measures were approved by all 85 deputies present in the 100-seat regional assembly.
Crimea's lawmakers also asked the United Nations and other countries to recognize the newly declared independence.
A delegation was heading to Moscow for talks on how to proceed.
The moves follow a disputed referendum in which voters in the Russian-occupied peninsula overwhelmingly supported becoming part of Russia.
Kyiv, the United States, European Union, and other governments have dismissed the referendum -- conducted with thousands of heavily armed Russian troops and pro-Moscow "self-defense" forces patrolling Crimea -- as illegitimate.
EU foreign ministers gathered in Brussels on March 17 responded with a decision to impose sanctions against 21 officials from Ukraine and Russia in retaliation for their part in Russia's seizure of Crimea and the secession referendum.
The EU sanctions -- agreed after a three-hour meeting -- include travel bans and asset freezes. Lithuanian Foreign Minister Linas Linkevicius said on Twitter that more measures are likely to follow in the coming days.
RFE/RL's correspondent says they are expected to expand the list to include more senior figures closer to Russian President Vladimir Putin.
EU foreign policy chief Catherine Ashton said Europe needed to send the "strongest possible signals" to Russia.
"We have an 'anschluss' of Crimea which cannot go unanswered by the international community," Polish Foreign Minister Radoslaw Sikorski said before the gathering. "The referendum was not constitutional, nor legal, and the choice of Crimea will not be recognized by the international community. And this means that the EU will do what it said it will."
In the United States, President Barack Obama has ordered asset freezes against seven Russian officials, including two presidential aides, in retaliation for the occupation of Crimea.
Obama also imposed similar measures against four Ukrainian nationals, including ousted President Viktor Yanukovych, who is in Russian exile.
Russia says the referendum complies with international law.
The Kremlin said Putin would address Crimea's possible accession in a speech to a joint session of the Russian parliament on March 18.
Senior Russian lawmakers have suggested that formally annexing Crimea is just a matter of time.
Crimean lawmakers on March 17 declared that all Ukrainian state property would become the property of the Crimean Republic.
Parliament also introduced the Russian ruble as a second official currency alongside the Ukrainian hryvnya. It said the hryvnya could be used in Crimea until January 1, 2016.
The speaker of the Crimean parliament, Vladimir Konstantinov, was quoted as saying Ukrainian military units in the region would be disbanded.
Crimean Prime Minister Sergei Aksyonov tweeted that the region would switch to Moscow time on March 30.
Meanwhile, Ukraine's parliament on March 17 endorsed a presidential decree to carry out a partial mobilization involving 40,000 reservists.
Officials in the Ukrainian government that took office after Moscow-backed President Viktor Yanukovych fled to Russia in late February have vowed not to cede "one centimeter" of Ukrainian territory.
They have sought the arrest of senior separatist officials in Crimea and the Ukrainian parliament voted on March 15 to dissolve the Crimean Supreme Council, the regional parliament on the peninsula.
Ukrainian Prime Minister Arseniy Yatsenyuk on March 16 pledged "with our Western partners...[to] do everything possible to make sure that everyone, who today feels protected enough by Russian guns to do whatever they please, knows that they will have to answer for separatism and attempts to destroy the constitutional order." He added, "No place in the world will be safe enough for them to disregard the law. And Russia will not save them."
The republican parliament on March 11 voted for the union with Russia, claiming it had immediate effect but that the referendum would cement its case.
Crimean authorities said 96.8 percent of voters in the March 16 referendum backed secession from Ukraine and Russian union.
Turnout in the referendum was said to have been 82 percent, although many pro-Kyivan Ukrainians and Crimean Tatars were expected to boycott the vote.
Crimean referendum commission chairman Mykhaylo Malyshev said his office had received no official complaints about violations.
But Andriy Krysko, chairman of the Crimean branch of the Voters Committee of Ukraine, told RFE/RL's Ukrainian Service
that there were numerous election violations, including voting by "dead souls" on aged voter lists. Krysko also said there was an "abnormally high" number of voters registering under a simplified, on-the-spot procedure at polling stations.
Other groups, including a Crimean Tatar organization, noted further violations (in Ukrainian here
AFP news agency said its journalists and others were blocked from entering polling stations in Sevastopol and in Simferopol.
Russian forces since late last month have been occupying Crimea, where there are currently some 22,000 troops, according to Ukraine's acting defense minister. Thousands more pro-Russian "self-defense" troops have been mobilized, including by the republic's breakaway authorities.
Voters in the referendum were asked whether Crimea -- where ethnic Russians are about 60 percent of the population -- should break away from Ukraine and become part of Russia, or opt for greater autonomy.
Based on reporting by RFE/RL's Ukrainian Service, RFE/RL correspondent Rikard Jozwiak in Brussels, and Reuters, AFP, and Interfax