Turkish police on Monday fired tear gas and plastic bullets at protesters seeking to march to Istanbul's Taksim Square to celebrate May Day, in defiance of an official ban.
Istanbul police authorities said on Monday they arrested 165 people in connection with the protests, including 139 people for "unauthorised marches".
Police tried to stop around 200 protesters in the Gayrettepe district on the European side of Istanbul who wanted to walk to the famous Taksim square in spite of the ban by city authorities, an AFP journalist said.
The protesters -- made up of left-wing groups -- unfurled anti-government banners against the result of the April 16 referendum, which handed President Recep Tayyip Erdogan expanded powers.
"Long Live May Day, No to dictator!" the banners read.
Turkish authorities imposed a ban on any demonstration at Taksim square, with police sealing off the avenue with barricades and halting traffic.
Among those detained were two women who attempted to penetrate the ban and unfurl banners at the square, the private Dogan news agency reported.
In a statement, the Istanbul police headquarters said 17 people who tried to open banners were among those detained.
Police had also seized 85 Molotov cocktails, 95 paint-filled bottles, 25 fireworks and several masks on Sunday and Monday in Istanbul.
In the meantime, several thousand people and unions attended celebrations in an officially sanctioned rally in the Bakirkoy district near the international airport on the city's western side.
- 30,000 police in charge -
Some 30,000 police were on duty in Istanbul alone, with the governor's office urging citizens not to heed calls for protests in non-official areas.
Police checked tourists and citizens passing through Taksim and all streets leading to the square were cordoned off with iron barricades.
Metro lines did not stop at Taksim square, which was a rallying ground for May Day celebrations until 1977, when at least 34 people were killed during demonstrations.
Authorities later opened up the square for celebrations in 2010 but it was shut down again after it played host to anti-government protests in 2013 targeting Erdogan, then prime minister.
"Our people were massacred on May Day in 1977, workers were massacred," a protester who gave her name as Sevim told AFP.
"We are going to Taksim square because it is a meaningful place for the working class," she said shortly before the police intervention in Gayrettepe.
This year's May Day celebrations also come after the 'Yes' camp won last month's referendum with 51.41 percent of the vote against 48.59 percent for the 'No' camp.
The opposition have alleged major irregularities but its complaints were thrown out by the election commission and a top court.
Yunus Ozgur, another demonstrator, said he wanted to march to Taksim square to protest "irregularities" during the referendum.
"We are frustrated," he said. "Taksim has a political meaning. They (authorities) are scared of this. Taksim is ours."
In Ankara, at least 6,000 people demonstrated for May Day and against the referendum result, holding large letters spelling out "Hayir" meaning "No" in Turkish, an AFP photographer said.
Some held banners saying: "No means no".
Earlier in the day, up to 60 people commemorated the 103 people killed outside the train station in Turkey's worst terror attack in October 2015.