Turkeybs president has accused the government of acting outside the law after prime minister Recep Tayyip Erdoganbs administration banned Twitter, a measure the US has likened to bbook burningb.

President Abdullah Gulbs attack on the ban b imposed after Twitter was used to spread a series of corruption allegations against Mr Erdoganbs government b comes as Turkey steels itself for further leaks on the microblogging platform in the last days of a highly charged election campaign.

In a further development on Sunday, Turkey shot down a Syrian jet it said had crossed over into Turkish airspace, the latest in a series of clashes between the two neighbouring states.

Speaking on Sunday, Mr Gul said it was bnot legally possible to shut down the internet and platforms [such as Twitter]b, noting that the number of tweets emanating from Turkey had increased since the block was imposed on midnight on Thursday. His words went beyond criticism of the ban he had earlier voiced on Twitter itself.

But, addressing hundreds of thousands of supporters at rallies in the cities of Izmit and Istanbul, Mr Erdogan redoubled his criticism of social media. bI donbt understand how people of good sense could defend this Facebook, YouTube and Twitter,b the prime minister said. bThere are all kinds of lies there.b He accused Twitter of fomenting unrest in Ukraine and Egypt as well as in Turkey itself by ignoring national laws under the name of freedom.

Mr Erdoganbs government has tightened the ban since its initial introduction.

Many users in the country reported over the weekend that workarounds that had previously given them access to the site, such as changing the domain name information on computers, could no longer overcome the ban.

However, other methods, such as using virtual private networks, a technology whose use has soared since Turkey introduced the block, still proved effective.

Internationally, Turkey appeared increasingly isolated because of its stance, with many of its traditional allies rounding on the ban.

In a blog, the US State Department described internet censorship as b21st century book burningb and ba threat to freedom of speech everywhereb, calling for Turkeybs decision to be reversed.

Hillary Clinton, the former US secretary of state, also tweeted her condemnation of what she said was the bfundamental rightb to speak out and connect.

Although the move was initially depicted as a result of court orders, there is no specific court order to shut down access to Twitter wholesale. Instead, Turkeybs Telecommunication Authority imposed the ban hours after Mr Erdogan announced his intention to broot out Twitterb and added that he did not care what the international reaction was.

Many lawyers say it is illegal and disproportionate under Turkish law to block the entire Twitter site, even though Mr Erdoganbs government recently passed new legislation in response to the leaks that increases its control over internet access.

Mr Erdogan faces local elections on March 30 which he has depicted as a virtual referendum on his rule and the final word on his battle with the movement of Fethullah Gulen, an Islamic preacher with followers throughout Turkish institutions. Mr Erdogan blames Mr Gulenbs movement both for the leaks on Twitter and an associated corruption probe into his circle of intimates, now largely stalled by government action.

The prime minister has described some of the postings as fabricated b such as a voice recording in which he appears to tell his son to hide large amounts of money from a corruption probe b while acknowledging others as authentic but illegally recorded.

In a note, the prime ministerbs office said that Twitter had not complied with Turkish court rulings holding that certain accounts on the social network had violated peoplebs privacy. bIn order to prevent irremediable future grievances, access to Twitter has been blocked,b it added. bThe main ground for this measure is the continuous disregard of the court rulingsb .b .b .b Twitter has been used as a means to carry out systematic character assassinations by illegally acquired recordings, fake and fabricated records of wiretapping [and] continuing violation of personal rights.b