(Adds opposition challenge, Fuele, quotes, markets)
* Gul says only individual pages should be blocked
* On campaign trial, Erdogan vows to "wipe out" Twitter
* Regulator says ban follows court orders
By Orhan Coskun
ISTANBUL, March 21 (Reuters) - Turkish President Abdullah Gul set himself publicly at odds with Prime Minister Tayyip Erdogan on Friday, saying that it was unacceptable to impose complete bans on social media platforms such as Twitter.
Turkey's courts blocked access to Twitter following Erdogan's vow, on the campaign trail ahead of key March 30 local elections, to "wipe out" the service. In a defiant stand, Erdogan said he did not care what the international community had to say about it.
The prime minister, who has been in power for 11 years, is battling a corruption scandal that has been fed by social media awash with alleged evidence of government wrongdoing.
Gul, however, took to Twitter himself to say complete bans on social media platforms were unacceptable and to voice his hope that the block would be short-lived.
Turkey's main opposition party said it would challenge the ban and file a criminal complaint against Erdogan on the grounds of violating personal freedoms. The country's bar association filed a separate court challenge.
"One cannot approve of the complete closure of social media platforms," Gul tweeted. He said only individual Internet pages should be blocked if there is a court order on the grounds that a person's privacy is being violated.
Gul co-founded the ruling Islamist-rooted AK Party with Erdogan and has remained a close ally. But he is viewed as a more conciliatory figure than the combative prime minister and their relations have at times appeared strained.
In the run up to the elections, the president has been hesitant to openly criticise Erdogan, despite the brewing scandal and the latter's increasing claims of a conspiracy against his government
Erdogan's ruling AK Party has already tightened Internet controls, handed government more influence over the courts, and reassigned thousands of police and hundreds of prosecutors and judges as it fights a corruption scandal he has cast as a plot by political enemies to oust him.
Telecoms watchdog BTK said the social media platform had been blocked by the courts after complaints were made by citizens that it was breaching privacy. It said Twitter had ignored previous requests to remove content.
"Because there was no other choice, access to Twitter was blocked in line with court decisions to avoid the possible future victimization of citizens," it said.
Twitter users in Turkey began reporting widespread outages in direct connections overnight. Some users trying to open the Twitter.com website were taken to a statement apparently from another regulator citing four court orders as the basis for the ban.
European Union Enlargement Commissioner Stefan Fuele said he was "gravely concerned" by the move.
"Being free to communicate and freely choose the means to do it is (a)fundamental EU value," Fuele wrote on his Twitter account.
Turkey's financial markets were also unsettled, with the lira weakening to 2.24 against the dollar, shares falling 0.7 percent and the benchmark 10-year bond rising to 11.24 percent from 11.12.
San Francisco-based Twitter said it was looking into the matter but had not issued a formal statement. The company did publish a tweet addressed to Turkish users instructing them on how to continue tweeting via SMS text message.
Erdogan was scathing about the social media service on Thursday
"Twitter, mwitter!," he told thousands of supporters at a rally, in a phrase translating roughly as "Twitter, schmitter!".
"We will wipe out all of these," Erdogan said. "The international community can say this, can say that. I don't care at all. Everyone will see how powerful the Republic of Turkey is," he said in a characteristically unyielding tone. (Writing by Daren Butler Editing by Jeremy Gaunt)