SIMFEROPOL, Ukraine — The prime minister of Crimea, the autonomous Ukrainian republic seized by Russian military forces, said Tuesday that most Ukrainian military units on the Crimean Peninsula had surrendered and pledged allegiance to his pro-Russian government, and that local officials were working to speed up a referendum on independence from Ukraine.

Speaking at a news conference on Tuesday morning, Prime Minister Sergei Aksyonov said that Crimean officials were in control of the security situation, even as standoffs continued between Russian forces and Ukrainian troops at several military installations, including at a base near the Belbek airport, near Sevastopol.

“There is no safety threat to human life in Crimea,” Mr. Aksyonov said.

In Kiev, the Ukrainian Defense Ministry flatly denounced the assertion of defections. “This information is false,” the ministry said in a statement, adding: “All the Ukrainian military units, formations and warships stay in their permanent locations. Ukraine’s military controls the territories of their military posts.”

It was not possible to independently verify Mr. Aksyonov’s claims, and even he did not assert that all military units were now aligned with his administration. Yet the Defense Ministry’s blanket denial — “all of the servicemen serve the Ukrainian people and do not even consider the proposals to defect” — was dubious as well.