SIMFEROPOL, Crimea — A power failure plunged much of the Crimean capital, Simferopol, into darkness on Monday, the second partial blackout in two days, as the Ukrainian government in Kiev appeared to retaliate against Russia’s occupation and annexation of the peninsula by sharply cutting electricity supplied from the mainland.

Homes and businesses went dark across a large swath of the city, underscoring the vulnerability of the geographically isolated peninsula, which is dependent on mainland Ukraine for many vital services, including electricity and much of its water supply.

Officials here and in Moscow had anticipated such a move by the Ukrainian government. In recent days, regional officials said they had acquired 900 generators to provide electricity to vital buildings, including hospitals. It was not immediately clear if those generators were in use.

The state-run Ukrainian national energy company, Ukrenergo, issued a statement attributing the blackouts in Crimea to emergency repairs to two major transmission lines.