MOSCOW, May 4 (Reuters) - Russian President Vladimir Putin and German Chancellor Angela Merkel discussed the Ukraine crisis in a telephone call and stressed the importance of "effective international action" to reduce tension, the Kremlin said on Sunday.
The leaders also discussed the supply of Russian gas and its transit, based on the results of a recent meeting in Warsaw. In Warsaw on Friday, Russia threatened to cut natural gas supplies to Ukraine in June if it receives no prepayment in an escalating row between Moscow, Ukraine and the European Union over energy supplies.
(Reporting by Megan Davies, editing by Elizabeth Piper)