* PM says opposition, Islamic cleric form 'alliance of evil'
* Anonymous recordings on YouTube purportedly expose graft
* Turkey holds municipal elections on March 30 (Recasts with Erdogan rally)
By Nick Tattersall
ISTANBUL, March 23 (Reuters) - Turkish Prime Minister Tayyip Erdogan rallied hundreds of thousands of supporters on Sunday, dismissing accusations of intolerance by Western and domestic critics. "I don't care who it is. I'm not listening," he said to cheers.
Erdogan, tackling a corruption scandal that could damage his AK Party at local polls next Sunday, used a speech in the western city of Izmit also to announce Turkish forces had shot down a Syrian fighter that had crossed into Turkish air space.
Supporters waved red Turkish flags and blue and gold emblems of the AK Party he founded in 2001 and led to power a year later vowing to root out the corruption that had dogged rivals.
Western nations and rights groups have accused Turkey of intolerance for closing down the Twitter networking site over anonymously posted audio tapes that implicate Erdogan in graft. Erdogan says tapes of phone conversations had been manipulated as part of a smear campaign.
"The usual media are attacking us. What do they call it? 'Intolerance of freedoms'," he said . "I don't care who it is, I'm not listening. Even if the world stands up against us, I am obliged to take measure against every attack that threatens my nation's security.
"This entity called Twitter, this YouTube, this Facebook, they have shaken families to their roots...I don't understand how people of good sense could defend this Facebook, YouTube and Twitter. There are all kinds of lies there."
Erdogan accuses Islamic cleric Fethullah Gulen, a former ally who helped him drive reforms including the taming of the armed forces, of leading a campaign to blacken his name and topple him. At a campaign speech on Saturday he described Gulen's network, which has influence in the police and judiciary, as a terrorist organisation.
The dramatic power struggle that has broken out between Erdogan and Gulen has undermined Western perceptions of NATO member Turkey as an exemplary Muslim democracy and a possible anchor of stability in the Middle East.
Erdogan, his picture shown on banners across the country, draws heavily on his image as the strong leader Turkey has long lacked. His supporters cherish the idea still while many critics feel strength has mutated to authoritarianism.
With familiar flourish Erdogan announced to the crowd Turkish forces had shot down a Syrian plane
"A Syrian plane violated our airspace...Our F-16s took off and hit this plane. Why? Because if you violate my airspace, our slap after this will be hard."
Rebels have been fighting for control of the Kasab crossing, the border region, since Friday, when they launched an offensive which Syrian authorities say was backed by Turkey's military.
Syria said Turkish air defences shot down the jet while it was attacking rebel forces inside Syrian territory, calling the move a "blatant aggression".
While Erdogan spoke in Kocaeli, hundreds of thousands of supporters gathered on the shores on the Sea of Marmara in Istanbul on the approaches to the Bosphorus Strait for what will be the climax of the electoral campaign.
Next Sunday's vote could yet decide the future of a man who at first won plaudits in the West and Middle East for his economic success and reforming drive, but has more recently come under heavy criticism as, in the eyes of many, an authoritarian, increasingly intolerant leader.
Not that all would share that view or be swayed by the accusations of corruption against him and his party. Erdogan remains by far the most popular politician and hopes to match or exceed the 40 percent vote AK received at local polls in 2009.
There is widespread expectation of further postings intended to damage Erdogan, who denies all graft accusations. These could emerge ahead of the local polls, where any result significantly below 40 percent could undermine his position and his prospects of election to a powerful presidency later this year.
But they could also emerge during the presidential election period itself. There is no open sign of any move against Erdogan in the AK Party but a poor result next week could revive concern that emerged over his hard line against protesters last summer.
Ultimately, much could hinge on the opposition regaining the leadership and momentum it has lacked since 2002. Then, Erdogan drew on public anger over corruption in Turkey's old political elite, naming his new party AK, an acronym for Justice and Development but also a word meaning clean or white.
(Additional reporting by Humeyra Pamuk, Seda Sezer in Istanbul; writing by Ralph Boulton, editing by Daren Butler; Editing by Gareth Jones)