Twitter has limited access to a tweet by Turkey’s interior minister who referred to student protesters as “LGBT perverts”.

For weeks, students and staff at Istanbul’s prestigious Bogazici University have been protesting against President Recep Tayyip Erdogan’s appointment of Melih Bulu, a figure who has links to his ruling party, as the university’s rector.

They have been calling for Mr Bulu’s resignation and for the university to be allowed to elect its own president.

Late on Monday, police clashed with demonstrators who staged protests demanding the release of a group of students who were arrested over the weekend on charges of inciting hatred and insulting religious values for a poster displayed at Bogazici University, that depicted Islam’s most sacred site with LGBT flags.

Authorities said 159 people were detained in the clashes, although several were later released.

Turkey’s interior minister Suleyman Soylu tweeted on Sunday that “LGBT perverts” had been detained for “disrespecting the Great Kaaba”.

On Tuesday, he repeated the slur, saying on Twitter that the Turkish government would not tolerate “LGBT perverts who attempted to occupy the rector’s office”.

That prompted Twitter to place Mr Soylu’s tweet behind a notice warning that his message violated the social media platform’s rules about “hateful conduct”.

Twitter said, however, it had decided to allow people to click to view Mr Soylu’s tweet on grounds that it was in the public’s interest to have access to a tweet by the elected politician.

Mr Erdogan himself levelled criticism at the protesters during a speech on Monday, by praising the youth wing of his conservative and Islam-oriented party for not being like the “LGBT youth”.

Meanwhile, police in Istanbul used tear gas and rubber bullets to break up a new demonstration to denounce Mr Bulu’s appointment, Halk TV television reported. The station’s reporter was slightly hurt in the melee.

Police in the capital, Ankara, also dispersed a demonstration by students who gathered near the city’s main square in a show of solidarity with the Bogazici students. At least 69 demonstrators were detained, Halk TV television reported.

Read more: Students arrested in Turkey over Mecca poster with LGBT flags

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 criminalise 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 victimisation.”

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 organisation 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.”