Istanbul, Turkey - President Recep Tayyip Erdogan has welcomed the "Yes" vote in the referendum to amend Turkey's constitution and grant the country's presidential office new executive powers.

"We have been attacked by other nations of the world. You have seen how the West attacked us," Erdogan told cheering supporters in Istanbul on Sunday.

"We have not been divided … We have already been on our way, now we will gear it up [with the new system]," he said. "We have so much work to do in this country."

The constitutional changes were backed by Erdogan, the Justice and Development Party (AK Party) founded by him, and the leadership of the Nationalist Action Party (MHP), whose parliamentary support was vital to take the amendments to a public vote.

READ MORE: Turkey referendum - Erdogan's AK Party claims victory

Speaking before Erdogan, Prime Minister Binali Yildirim thanked the Turkish people for their decision to back the constitutional amendments.

"We are all brothers and sisters in a single body standing against traitors," Yildirim said, speaking at the headquarters of his governing AK Party in Ankara.

"Thank you Turkey, thank you my holy nation … The nation said the last word and said 'Yes'," he said.

The "Yes" campaign won with 51.4 percent of the vote with 100 percent of ballots counted, according to the unofficial results.

The main opposition Republican People's Party (CHP) demanded a recount, citing voting irregularities. There were demonstrations in various parts of Istanbul until morning challenging the referendum's results.

The new constitutional changes transform Turkey's governance from a parliamentary system to an executive presidency, significantly expanding the powers of the top office.

The result gives the president to be elected in 2019 new powers to appoint vice-presidents, ministers, high-level officials, and senior judges.

It will also allow the president to dissolve parliament, issue executive decrees, and impose states of emergency.

Speaking to Al Jazeera outside the AK Party headquarters in Istanbul, Erdal Erdinc Durucu, 37, said Erdogan has started a new age for Turkey, and ended another.

"Until today, our hands were tied. Our president has been trying to do many good things for us. But different powers tried to prevent him from doing so," Durucu said.

"The recent coup attempt was the latest example of this. God willing, we beat this attempt like others … Turkey is ready to rule the world now. The Ottoman Empire is coming back."

INTERACTIVE: How will Turkey change if it votes 'Yes' on April 16?

Another supporter, Yasemin Ozgen, a 43-year-old housewife, said: "Good days are coming. With this result, Turkey will break away from Europe as a strong power by itself. An independent Turkey will take its own decisions and will use its resources."

There is growing negative sentiment against the European Union in Turkey as Ankara's relations with the bloc, particularly member states Germany and the Netherlands, have been tense since last month. Those two nations barred Turkish ministers from holding referendum campaign rallies within their borders, where millions of Turkish voters live.

Turkey has been under a state of emergency since a group in the Turkish army tried to overthrow the government in a failed coup attempt in July 2016 that killed around 300 people in total.

In recent years, bomb attacks claimed by, or blamed on, Kurdish fighters' groups and the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) have killed hundreds of security forces and civilians.

Turkey's presidency has traditionally been a largely neutral and ceremonial role, without many political responsibilities, as specified under the current constitution.

However, Erdogan has effectively transformed the office into a more politically active one since he became Turkey's first president to be elected by popular vote in 2014, following prior constitutional changes passed in a similar referendum in 2010.

The main opposition CHP, the pro-Kurdish People's Democracy Party and other critics argue that the amendments give too much power to one individual, undermining the separation of powers in the government.

Additional reporting by Cagan Orhon

Follow Umut Uras on Twitter: @Um_Uras