Turkish electoral board head says "yes" campaign won referendum

ANKARA, April 16 (Reuters) - Unofficial results show that Turks approved changes to their constitution handing President Tayyip Erdogan sweeping new powers in a referendum on Sunday, the head of the country's High Electoral Board (YSK) said.

The "yes" campaign won 1.25 million more votes than the "no" campaign and with only around 600,000 votes still to be counted that meant the changes had been approved, YSK Chairman Sadi Guven told a news conference in Ankara.

He said the YSK had decided to consider unstamped ballots as valid unless they were proved to be fraudulent, after a high number of complaints - including one from the ruling AK Party - that its officials had failed to stamp some ballot papers.

The "no" campaign has said the last-minute decision raises questions about the validity of the vote. But Guven said the decision was taken before results were entered into the system, and that members of the AKP and the main opposition were present at almost all polling stations and signed off on reports.

He said official results were expected in 11-12 days.

(Reporting by Tuvan Gumrukcu and Ece Toksabay; Writing by Nick Tattersall)