MOSCOW, April 29 (RIA Novosti) - Russian President Dmitry Medvedev signed on Thursday a law on the ratification of a Black Sea Fleet agreement with Ukraine, the Kremlin said.

Earlier on Thursday Ukrainian President Viktor Yanukovych signed a similar law.

The agreement extending the lease on the Russian Navy base in the Ukrainian port of Sevastopol for 25 years after the current lease expires in 2017 was earlier ratified by the Russian and Ukrainian parliaments.

In return for the lease extension, which may be extended for an additional five years, Ukraine will receive a 30% discount on Russian natural gas that will be worth an estimated $40 billion.

Experts say the deal demonstrates the new atmosphere of cooperation between Russia and Ukraine, after relations plunged to post-Soviet lows under the previous Ukrainian president, Viktor Yushchenko.