Polls have opened in Turkey in a national referendum over whether or not to approve the government's proposed series of 26 amendments to the country's constitution. Prime Minister Recep Tayyip Erdogan has spearheaded the ruling Justice and Development Party's (AKP) campaign in favor of the reform package, arguing that the 26 amendments will bring greater freedom and democracy. "Can there be anything wiser and more meaningful than going from a coup constitution to the constitution of the people?" Erdogan said in an interview with CNN, referring to the fact Turkey's current constitution was introduced in the wake of a military coup on September 12, 1980 -- 30 years to the day before Sunday's vote. Erdogan was speaking aboard his campaign bus as he toured Istanbul on Friday in a last-minute pitch to voters. Thousands of enthusiastic supporters greeted him as he attended Friday prayers at a mosque on the outskirts of the city, chanting "Evet!" -- yes in Turkish and the slogan for those supporting constitutional change.