* Tatars say Russia refuses to re-register TV station
* Tatars opposed Russian annexation of Crimea
* Turkey denounces abuse of Tatars' rights on peninsula
By Richard Balmforth and Pavel Polityuk
KIEV, April 3 (Reuters) - The silencing of a TV station for the Tatar people in Crimea, annexed by Russia from Ukraine a year ago, sparked an outcry on Friday, with Kiev accusing Moscow of trying to stamp out non-Russian influence on the peninsula.
The station, ATR, which formerly broadcast under a Ukrainian licence, has sought four times to re-register with Russia's media regulator, Roskomnadzor, to stay on the air. But each time it was turned down because of alleged mistakes in its applications, Tatar officials said.
The station, which broadcast in the Tatar language to what officials say was an audience of 4 million people in Crimea and beyond, went off the air just after midnight on April 1 rather than face fines of up to $90,000.
There was no immediate comment from Roskomnadzor in Moscow.
The Tatars, a Muslim people who are indigenous to the Black Sea peninsula and number about 300,000 in Crimea's population of two million, opposed the Russian annexation in March 2014, which followed the overthrow of a Moscow-backed president in Kiev.
Tatar officials saw the refusal to re-register ATR as an attempt to silence their critical stance of Russian rule there.
"It's obvious that the (Russian-backed) authorities have no interest in registering the channel. They are finding formal pretexts for denying it," Ibraim Umerov, a press aide to one of the Crimean Tatar leaders, told Reuters.
Speaking in Lithuania, Turkish Foreign Minister Mevlut Cavusoglu decried rights abuses against the Turkic-speaking Tatars and said Ankara would send an informal observer mission to the peninsula soon.
"The Crimean people and particularly Crimean Tatars have been oppressed, attacked and their rights have been violated ... We are sending an informal mission to observe human rights violations in Crimea soon," he told journalists.
Ukraine's foreign ministry, in a strongly-worded statement, said the move to close down ATR had clearly been undertaken "with the knowledge and on the instruction of the Kremlin."
"These actions are a cynical and deliberate strategy of Russia aimed at consistently squeezing everything Crimean Tatar and everything Ukrainian from the cultural, informational and political space of the occupied peninsula," the statement said.
Human rights organisations said the silencing of ATR was part of a pattern of stifling Crimean Tatar language outlets and other pro-Ukraine media there.
Re-registration had also been refused to the radio station Maydan, a website 15minut.org and two newspapers, Amnesty International said. A popular children's television channel had also been closed down.
The New York-based Human Rights Watch said that since annexation, Crimea's new authorities had carried out raids on several media outlets, confiscating and damaging equipment. Several journalists and bloggers critical of the authorities had been detained, harassed or attacked, it said in a statement. (Additional reporting by Andrius Sytas in Vilnius; Writing By Richard Balmforth; Editing by Crispian Balmer)