KIEV, May 21 (Reuters) - Ukrainian President Volodymyr Zelenskiy extended sanctions against companies and politicians blamed by Kyiv for involvement in Russian aggression against Ukraine, his office said on Friday.

The list of hundreds of entities includes Russian television channels, news agencies, newspapers, consulting companies, online payment system WebMoney, and leaders of pro-Russian separatists. They are prohibited from conducting business in Ukraine, using their assets or withdrawing capital.

Relations between Moscow and Kyiv collapsed after Russia annexed the Ukrainian region of Crimea in 2014 and Russian-backed separatists took control of a chunk of eastern Ukraine that same year. Kyiv says the fighting in the eastern region of Donbass has killed 14,000 people in seven years.

Tensions have flared again in recent months after the two countries traded blame for a violation of a ceasefire agreement in Donbass, and Russia, in what it called a defensive exercise, massed troops on its western border with Ukraine and in Crimea.

Zelenskiy said Russia had deployed more than 100,000 military personnel near the Ukrainian border and continued to maintain them despite a promise to withdraw troops.