By Humeyra Pamuk and Daren Butler

ISTANBUL (Reuters) – Every Saturday for 23 years, dozens of people have held a vigil in a central Istanbul square, sitting in silence and holding pictures of relatives who went missing in police detention.

The group was about to stage their 700th demonstration last Saturday when Turkish police told them their protest was banned, before firing tear gas and plastic pellets to disperse the crowd and detaining dozens – including a 82 year-old woman who was among the first to protest in 1995 in search of her son.

The sit-in by the so-called Saturday Mothers was one of the few remaining public protests near Istanbul’s Taksim square, once a vibrant demonstration ground but now off-limits for opposition groups.

Critics say that breaking up the vigil was another sign that NATO member Turkey is drifting into more authoritarian rule under President Tayyip Erdogan, adding to Ankara’s already deteriorating record on human rights and media freedoms.

Casting the protest as a cover for supporting terrorism, Interior Minister Suleyman Soylu said the Saturday Mothers were linked to the outlawed Kurdistan Workers Party (PKK) and hinted the vigils would no longer be allowed.

“This has been one of Turkey’s oldest civil disobedience movements,” said Ahmet Sik, former journalist and a lawmaker for the pro-Kurdish Peoples’ Democratic Party (HDP), who was at Saturday’s protest.

“There was a time when the police helped these people to do their vigil. To criminalize such an established protest now is an attempt to intimidate the rest of the public,” he said.

Turkey in July lifted a two year-long state of emergency during which 150,000 civil servants were purged and 77,000 people suspected of links to a failed coup in 2016 were charged.

But opponents say Erdogan’s new executive presidency and a counter-terrorism law passed last month equips him with sweeping powers to stifle opposition.

Soylu said on Monday that authorities blocked the sit-in because participants were “trying to create victims through motherhood and mask terrorism through that victimization.”

At a news conference in Istanbul, the group denied links to any militant group and pointed out Erdogan, when he was prime minister in 2011, met them and pledged support.

They also vowed to continue their protest.

“Nobody is using us. Nobody has made us come here,” said Hanife Yildiz, whose son Murat went missing in police detention in 1995.

“I handed over my son to the state and I haven’t gotten him back since.”

‘REPEAT OF THE 1990s’

The silent vigils of Saturday Mothers began as a protest against what they say was the disappearance of relatives in police detention and extrajudicial killings in the 1990s.

At the time, when conflict with the Kurdistan Workers Party (PKK) was at its height, such disappearances and killings were common, mostly in Turkey’s mainly Kurdish southeast.

Emine Ocak, who was briefly detained on Saturday, was among those at the first sit-in after her son Hasan Ocak went missing following clashes with police in Istanbul in 1995.

Soylu rejected that Ocak had gone missing in detention and said he was a member of an ultra-leftist terrorist organization and that he was killed after a row within the group but the Saturday Mothers were trying to put the blame on the state.

Emine Ocak’s picture – the image of a white-haired elderly woman shouting as she was taken by riot police – went viral across Twitter. Her son Huseyin, Hasan’s brother, told Reuters police intervention was unexpected.

“There seems to be a new security approach in the state that very much resembles the one in the 1990s,” Huseyin Ocak said.

“I was there at the meeting with Erdogan on Feb 5, 2011. He said, ‘your problem is my cabinet’s problem.” He also promised to find our relatives, he added.

State investigations have shed light on some of the cases pursued by the Saturday Mothers. A 2011 parliament report found that Cemil Kirbayir, who went missing during a 1980 coup, died under torture.

“Since 1995 we have continued our rightful and silent resistance,” Cemil’s brother Mikail said. “You will not be able to remove us from that square.”

(Editing by Dominic Evans and Alexandra Hudson)