German Chancellor Angela Merkel urged Turkey on Thursday to answer questions raised by European observers over the presidential referendum, also said the EU must reflect on what future ties it wants with Ankara.
"The Turkish government must measure itself based on this report and answer the questions raised in it. We will very carefully follow how Turkey deals with reports of possible irregularities," Merkel told Parliament.
Organisation for Security and Cooperation in Europe (OSCE) and the Council of Europ monitors found that up to 2.5 million could have been manipulated in the close vote that went in President Recep Tayyip Erdoğan's favour.
EU-Turkey relations have been severely hit by actions taken by Erdoğan's government, she said.
"The developments over the past weeks have severely hit German-Turkish ties as well as European-Turkish relations," Merkel told parliament, saying in particular that Ankara's arrest and treatment of German newspaper correspondent Deniz Yücel was "incompatible with a constitutional state".
Some German conservative politicians have called on the European Union to end talks with Turkey about membership of the bloc, saying that failing to draw consequences after the referendum vote would hurt Europe.
She said it was "neither in Europe nor Turkey's interest" for either side to turn away from the other. "We will work towards returning to dialogue."
Merkel later told broadcaster NDR it was important to maintain dialogue with Turkey, given common security interests, and that the EU must forge a joint position on future ties.
"We have to be smart and clear," she added.
Merkel said she would also use a summit with fellow EU leaders in Brussels on Saturday to discuss "which measures would be appropriate" for the bloc to take vis-a-vis Turkey.
