Turks on Sunday voted by a narrow 51.4 percent margin to change their constitution and grant President Tayyip Erdogan sweeping new powers. The main opposition party has demanded the result be nullified, saying the voting was marred by irregularities.
Cezar Florin Preda, head of the delegation from the Parliamentary Assembly of the Council of Europe that monitored the vote, made the comments at news conference in Ankara. Turkey is a member of the Council of Europe.
Preda was joined by Tana de Zulueta, head of another team of international observers, who said the referendum fell short of international standards.
Turkey's High Electoral Board made a last-minute decision on Sunday to count ballots that had not been stamped by officials.