Voting is under way in Turkey in a landmark referendum that will determine whether President Recep Tayyip Erdogan will be granted sweeping new powers, BBC reports. 

Mr Erdogan's supporters say replacing the parliamentary system with an executive presidency would modernise the country, but opponents fear it could lead to greater authoritarianism.

A "Yes" vote could also see Mr Erdogan remain in office until 2029.

There have been reports of gunfire at a polling station in Turkey's south-east.

Two people were killed and one wounded in the incident in Diyarbakir province, the Hurriyet daily reports, saying the violence was sparked by "differing political views".

About 55 million people are eligible to vote across 167,000 polling stations, with the results expected to be announced late on Sunday evening.

Opinion polls suggest a narrow lead for "Yes".