UPDATE 1-Republican U.S. lawmakers seek tougher sanctions on Russia

(Adds firms targeted by sanctions)

WASHINGTON, April 30 (Reuters) - Nineteen Republican U.S. senators introduced legislation on Wednesday proposing broader and tougher measures to punish Russia over the Ukraine crisis, including sanctions on major banks and energy companies, as well as $100 million in military aid for Kiev.

The package would also require President Barack Obama to increase substantially U.S. and NATO support for the armed forces of Poland, Estonia, Lithuania and Latvia and accelerate implementation of missile defense in Europe.

Backers of the bill included Senator Bob Corker of Tennessee, John McCain of Arizona and other leading Republican foreign policy voices. They said sanctions announced so far by Obama had not gone far enough, and wanted immediate new sanctions on any Russians involved in the occupation of Crimea.

The bill also seeks immediate new sanctions on four Russian banks: Sberbank, VTB Bank, VEB Bank , Gazprombank, as well as energy firms Gazprom, Novatek and Rosneft, and Rosoboronexport, a major Russian arms exporter.

The lawmakers said they introduced the bill in the hope that it would push Obama to respond more forcefully to the Ukraine crisis.

There was no immediate word on whether the Senate, which is controlled by Obama's fellow Democrats, would vote on the bill. Democratic aides said that neither Democratic leaders nor the Senate Foreign Relations Committee had seen the measure.

(Reporting by Patricia Zengerle; Editing by Sandra Maler and Eric Beech)