Turkey's outgoing premier Recep Tayyip Erdogan was Thursday sworn in as president to extend his decade-long rule, as opponents who accuse him of authoritarianism walked out of the ceremony.

Erdogan, 60, took the oath in Ankara to begin a five-year mandate in which he has vowed to build a "new Turkey" by pushing through a new constitution and driving on with an ambitious development program.

Turkey's ruling party on Thursday confirmed Foreign Minister Ahmet Davutoglu as the successor to Recep Tayyip Erdogan as premier and party leader, with both men vowing the handover would herald no change in strategy.

Erdogan, 60, is to be sworn in as president on Thursday and the approval of Davutoglu, 55, from the ruling Justice and Development Party (AKP) was a key step in a tightly-choreographed succession process.

Turkey's new premier and outgoing foreign minister Ahmet Davutoglu leaves his successor a troubled legacy after a bold policy to expand Turkish influence across the ex-Ottoman empire left the country painfully exposed to the Syria and Iraq crises.

Foreign Minister Ahmet Davutoglu, who will be Turkey's next prime minister, is a loyal ally of incoming president Recep Tayyip Erdogan and the chief architect of an assertive but increasingly controversial foreign policy.

Turkey's president-elect Recep Tayyip Erdogan on Thursday named Foreign Minister Ahmet Davutoglu to succeed him as ruling party leader and prime minister, promoting an ally who is expected to show unstinting loyalty to the new head of state.

The Turkish foreign ministry on Thursday angrily denied a newspaper report that Ankara was in talks with Islamic militants to hand over a historic tomb it controls in Syria in exchange for dozens of nationals held hostage in Iraq.

Turkish authorities on Tuesday arrested at least 25 police officers in the latest nationwide swoop to detain suspects alleged to have illegally wiretapped key government figures including Prime Minister Recep Tayyip Erdogan, reports said.

Police conducted raids in 12 cities across Turkey, including Istanbul as well as the western province of Izmir, as part of the investigation into the allegations of espionage and illegal wiretapping, the private Dogan news agency reported.

The Turkish authorities will thoroughly investigate a report that Germany has been spying on its NATO ally since 2009, a senior official said Sunday, saying the claims need to be taken seriously.

German weekly Der Spiegel reported that the German secret service the BND has been spying on Turkey since 2009, as well as accidentally intercepting at least one telephone conversation of US Secretary of State John Kerry.

Turkey's president-elect Recep Tayyip Erdogan said his ruling Justice and Development Party (AKP) will meet on August 21 to agree on his successor as party leader and prime minister, newspapers reported Friday.

Erdogan, who won presidential elections on August 10 in the first round, must by law step down not only as prime minister but also as AKP leader when he is sworn in as president on August 28.

Prime Minister Recep Tayyip Erdogan on Thursday warned supporters against allowing any split in Turkey's ruling party, as he prepares to become a strongman president later this month to extend his domination of the country.

In his first keynote speech since he declared victory in Sunday's presidential election, Erdogan rubbished suggestions he would rule as a dictator and vowed to reconcile Turkey's divided society.