Ukraine's Security Service has banned two Russian scientists from entering the country without offering any explanation.

The two Russians will not be able to visit Ukraine for one year starting from November 12, 2009 on the basis of Clause 25 of Ukrainian law that regulates the legal status of foreign citizens and stateless persons, a spokesman for the Security Service told Interfax.

The Russian Foreign Ministry has denounced the Ukrainian authorities' decision.

Scientists Vladimir Frolov and Yelena Meskova were stopped at Kyiv's Boryspil Airport.

They planned to attend a Kyiv-based international forum on key problems of youth policy of Ukraine and Russia that was organized by non-governmental organizations, the Russian ministry said.