Turkey will hold a referendum this spring on dramatically expanding President Recep Tayyip Erdogan's powers after a parliamentary vote early Saturday backed changes that could leave him in power until 2029.
The government insists the proposals to create an executive presidency will ensure simpler and more effective leadership, but critics fear they will edge Turkey toward one-man rule.
Hours after the bill was approved, Erdogan said the "real (and) final decision" would be made by the people in a referendum, expected to be held in April.
Parliament approved a new 18-article constitution, which includes the presidency changes, in a final vote which saw 339 in favour and 142 against.
Each article was put to a vote in the 550-seat parliament, where the ruling Justice and Development Party (AKP) enjoys a comfortable majority of 317 including the speaker.
At least 330 votes -- a three-fifths majority -- were needed to adopt the changes.
Speaking to supporters in Istanbul, Erdogan said he believed they would "move towards the future by working night and day" for the referendum campaign.
The bill would create an executive presidency for the first time in modern Turkey, giving the head of state the power to hire and fire ministers.
It would also abolish the post of prime minister for the first time, with the position to be replaced with a vice president, or perhaps several.
The changes prompted fractious debates with the assembly witnessing some of the worst fighting in years, including one altercation which broke out on Thursday after independent lawmaker Aylin Nazliaka handcuffed herself to the microphone.
The bill would allow parliamentary elections and presidential ballots to be held at the same time, with the draft giving November 3, 2019 as the poll date.
Prime Minister Binali Yildirim said the changes would allow for a "sole power that would be strong", meaning a more decisive approach to solving problems.
"There would be no weakness in fighting terror (or)... on economic issues," he told the TRT Haber broadcaster.
The proposed changes would also widen the scope of conditions in which the president can declare an emergency and would allow it to be in place for up to six months initially, up from 12 weeks.
Turkey has been under a state of emergency for almost six months following a failed coup in July that sought to overthrow Erdogan.
It was extended earlier this month, meaning that campaigning for the referendum will take place under the emergency, raising concerns among rights groups.
Emma Sinclair-Webb, Turkey director of Human Rights Watch, said she feared the public would not be sufficiently informed about the implications of the bill.
"There is no possibility under a state of emergency for an effective public debate in the media about the changes that are being brought in," she said.
The debate comes after a bloody year which saw multiple terror attacks by Kurdish militants and Islamic State (IS) militants.
On Saturday, an assailant opened fire on a police car in Istanbul, just hours after two rocket attacks in the city, targeting a police headquarters and the offices of the ruling AKP, local media reported.
No one was killed or injured, and no group claimed responsibility.
Opponents have accused Erdogan of marching towards authoritarian rule, comparing the executive presidency to sultans of the Ottoman Empire.
He was elected in August 2014 and the new constitution could mean the clock on his presidency will be reset to zero from 2019, meaning he could remain in power until 2029 rather than 2024.
Sinclair-Webb told AFP the changes could not be compared the system in countries like France or the United States because of their "strong checks and balances on the power", despite the government's insistence.
"According to the Turkish model that is outlined in this amendment, you don't have any such check on presidential power."
President of the Union of Turkish Bar Associations (UTBA) Metin Feyzioglu criticised the changes, saying they harked back to the country's Ottoman history.
"This new system is not unknown to us, because we have been ruled for 600 years in this way," he said.
"It has a name which is 'sultanate'.
"It is not a reform but suicide and the people will not commit suicide."