Erdoğan, who addressed his supporters in Kastamonu as part of election campaigning, left Kastamonu for Amasya in a helicopter briefly before the attack took place.

Sources from the Prime Ministry told the CNN Türk TV channel that one police officer had been killed and two others injured during a brief firefight between an armed group and police officers.

One police cruiser was also set ablaze. Special security teams were dispatched to the scene and police cordoned off the area.

Many ambulances were sent to the area, the broadcaster said. No further details were immediately available.

Addressing his supporters in Amasya, Erdoğan said terrorists who thought they couldn´t solve their problems at the ballot box think they will get results through armed attacks.

The prime minister said his party will not allow the division of Turkey and that it is doing everything it can to avert a confrontation among Turkey´s population of 74 million.

Observers say Erdoğan´s comments implied that the outlawed Kurdistan Workers´ Party (PKK) had orchestrated the attack.

The regulation, named “Procedures and Principles Regarding the Safe Use of the Internet,” brings four compulsory filtering options to Turkey´s Internet users, who will have to pick one of them. The filters are “family,” “child,” “domestic (inland)” and “standard.” The criteria by which websites will be filtered will be determined by the BTK. Circumventing these measures will be considered a crime and anyone doing so or attempting to do so will face heavy fines. Many websites are expected to be blocked by the filters irrespective of their content.

Similar measures attempting to control access to cyberspace are used in other countries, including China, Cuba and Iran, all notorious for Internet censorship. Arda Kutsal, owner of the popular blog webrazzi.com, argues in an article that the BTK move rivals China´s Golden Shield Project, aka the Great Firewall of China, a censorship and surveillance project carried out by the Ministry of Public Security of the government of the People´s Republic of China.

The issue of Internet censorship was already brought to public attention when a list of forbidden words was earlier announced as part of the regulations.

The news sparked a nationwide outcry as media reports on Tuesday referred to the date when the regulations will come into effect as the “death of the Internet.” Shortly after reports on the “death of the Internet” came out, Aug. 22 (22 Ağustos, in Turkish) became one of the hottest topics in Turkey and worldwide in social media.

Civil society has already launched campaigns against the new regulations. A website, imza.la, has started a campaign under the name “No to Aug. 22 Internet Coup” while thousands of people have joined events on Facebook protesting the filters.

In the meantime, the IPS Communication Foundation-Independent Communications Network (Bianet) filed a suit at the Council of State in April in order to stop the implementation of the new BTK regulations affecting access to the Internet. The foundation states in its petition that the new regulations lack legal grounds and limit without oversight basic rights and freedoms that are accepted by the Constitution and international conventions. The BTK has not yet issued a statement about the ongoing discussions.

In an interview with Austrian radio broadcast on Tuesday during a visit by Turkish President Abdullah Gul, Spindelegger said EU membership negotiations with Turkey would take years and serve to "Europeanise" the country.

"We will wait and see what happens, be contructive, but remain true to our basic position that we will strive for a special partnership with Turkey," he said.

Vienna´s official line is that the outcome of Turkish entry talks is open. Austrian voters would get the final say in a referendum if enough members of parliament seek one, as  resurgent far-right parties demand.

Turkish leaders are sounding increasingly frustrated over stalled progress in entry talks that began in 2005. Turkey, a growing economic power straddling Asia and Europe, says membership is its top foreign policy priority.

Ankara has already rejected the notion of a special partnership falling short of membership.

But the division of the Mediterranean island of Cyprus and reservations by heavyweights Germany and France about granting Muslim Turkey full membership are major obstacles.

Gul had called on Monday for a factual discussion of open points in the talks, criticised restrictions on EU visas, and urged the roughly 200,000 Turks in Austria -- half of them Austrian nationals -- to master German as well as Turkish.

In a radio interview aired on Tuesday Gul suggested booming bilateral business ties may suffer if Turkey continues to get the cold shoulder.

"One should ask whether Austrian companies will continue to be able to make the profits they make now in Turkey if they don´t cooperate with Turkey," he said.

He also addressed criticism of Turkey´s record on guaranteeing freedom of speech by saying: "In Turkey no journalist will be punished for his journalistic activity. No one will be sanctioned for his opinion."