MOSCOW -- Russia was swept up in patriotic fervor Friday in anticipation of bringing Crimea back into its territory, with tens of thousands of people thronging Red Square chanting "Crimea is Russia!" as a parliamentary leader declared the peninsula would be welcomed as an "equal subject" of Russia.

Ignoring sanctions threats and warnings from the U.S., leaders of both houses of parliament said they would support a vote by Crimeans to split with Ukraine and join Russia -- signaling for the first time that the Kremlin was prepared to annex the strategic region.

Tensions in Crimea were heightened late Friday when pro-Russian forces tried to seize a Ukrainian military base in the port city of Sevastopol, the Ukrainian branch of the Interfax news agency reported. No shots were fired, but stun grenades were thrown, according to the report, citing Ukrainian officials.

About 100 Ukrainian troops stationed at the base barricaded themselves inside one of their barracks, and their commander began negotiations, the report said. Crimea's pro-Moscow leader denied any incident at the base.

In the week since Russia seized control of Crimea, Russian troops have been neutralizing and disarming Ukrainian military bases on the Black Sea peninsula. Some Ukrainian units, however, have refused to give up. Crimea's new leader has said pro-Russian forces numbering more than 11,000 now control all access to region and have blockaded all military bases that haven't yet surrendered.

Only Tuesday, President Vladimir Putin said that Russia has no intention of annexing Crimea, though he has insisted that its residents have the right to determine the region's status in a referendum.

By Friday, however, Russian lawmakers were forging ahead with preparations for a possible annexation and welcoming a delegation from Crimea's regional parliament.

Valentina Matvienko, the speaker of Russia's upper house of parliament, made clear the country would welcome Crimea if it votes in the March 16 referendum to join its giant neighbor. About 60 percent of Crimea's population identifies itself as Russian.

"If the decision is made, then (Crimea) will become an absolutely equal subject of the Russian Federation," Matvienko said during a visit from the chairman of the Crimean parliament, Vladimir Konstantinov.

She spoke of mistreatment of Russian-speaking residents in Ukraine's east and south, which has been Moscow's primary argument for possible intervention.

The Russian parliament, meanwhile, scrambled to make it easier for Crimea to join Russia. Russia's constitution allows the country to annex territory only by an agreement "initiated ... by the given foreign government." That would entail signing an agreement with the new authorities in Kiev, whom Moscow doesn't recognize.

New legislation would sidestep that requirement, according to members of parliament, who initially said a new bill could be passed as soon as next week, but have since indicated that they will wait until after the referendum.

On the other side of Red Square from the parliament building, 65,000 people gathered at a Kremlin-organized rally in support of Crimea.

"We always knew that Russia would not abandon us," Konstantinov shouted. He also called on Moscow not to forget other Russia-leaning regions in Ukraine.

"We must not leave the Ukrainian people at the mercy of those Nazi bandits," he said, referring to the new government in Kiev.

The referendum has been denounced by Ukraine's fledgling new government in Kiev and President Barack Obama, who warned it would violate international law. The U.S. moved Thursday to impose its first sanctions on Russians involved in the military occupation of Crimea.

Foreign Minister Sergey Lavrov warned Secretary of State John Kerry that sanctions over Russian actions in Crimea could backfire, the ministry said in a statement. Lavrov urged the U.S. not to take "hasty, poorly thought-out steps that could harm Russian-U.S. relations, especially concerning sanctions, which would unavoidably boomerang on the U.S. itself," the statement said.