* Media outlets have taken sides in Ukraine conflict
* Russia's parliament calls on Kiev to release reporters
* Pro-Russia separatists have also detained journalists
By Thomas Grove
MOSCOW, May 21 (Reuters) - President Vladimir Putin called the detention of two Russian journalists in Ukraine unacceptable on Wednesday and suggested it highlighted wider questions about the legitimacy of political power in Ukraine.
The detention of the journalists, working for the pro-Kremlin Internet news outlet LifeNews, has added to tensions between Moscow and Kiev, which accuses Russia of destabilizing Ukraine's Russian-speaking east ahead of a presidential vote on Sunday.
"It's absolutely unacceptable and of course the question arises over the legitimacy of all political procedures in Ukraine," Putin said, speaking to journalists.
Ukraine's Defense Ministry said this week that soldiers had detained two unknown men who had identified themselves as journalists and were filming separatists.
Putin also dismissed as "nonsense" an allegation from the ministry saying the two journalists had been carrying portable air defense systems.
Both Ukrainian and Russian media have traded accusations of lying during the conflict.
Ukraine has temporarily blocked Russian television channels pending a court decision over their legality, but separatists who seized a television tower in eastern Ukraine have turned Russian channels back on, including Life News.
Pro-Russian separatists have also abducted a number of Ukrainian journalists, including Irma Krat who runs an online news outlet and Serhiy Lefter.
Russia's lower house of parliament, the Duma, passed a statement calling on Kiev to release the journalists Marat Saychenko and Oleg Sidyakin.
"We will succeed in freeing our two journalists and guarantee the freedom of their activities in Ukraine, including during large upcoming internal political events in Ukraine - the presidential election," said the Chairwoman of Russia's Upper House of Parliament Valentina Matvienko.
Pro-Kremlin TV channel RT also reported the detention of one of its contributing journalists, Graham Philips, though the information could not be independently confirmed. The British Foreign Office said it was aware of the detention of a British national, but would not confirm his name.
"We are in contact with the Ukrainian authorities and stand ready to provide consular assistance," said a Foreign Office spokeswoman.
Russia has repeatedly criticized the detentions saying that it shows Ukraine's lack of respect for press freedoms.
"This kind of lawlessness directed against Russian journalists, which has become a regular practice, confirms once again that the Ukrainian side is ignoring basic norms of democracy, in particular, freedom of speech," said a Foreign Ministry statement.
OSCE Representative on the Freedom of the Media Dunja Mijatovic called on both sides this week to stop targeting journalists.
(Additional reporting by Alexei Anishchuk in Shanghai, China and Natalia Zinets in Kiev; Kylie MacLellan in London; editing by Ralph Boulton)