Taoiseach Leo Varadkar has said he will use the office of Taoiseach to advance the cause of LGBT rights and to press for marriage equality across Ireland.

Mr Varadkar was addressing thousands of people attending the annual Pride festival in Dublin.

Organisers of Dublin LGBTQ Pride Parade said 30,000 people took part in this year's event.

Participants, including Mr Varadkar, began marching at 2pm, starting at St Stephen's Green, before finishing up in Smithfield.

CEO of Belong To, Moninne Griffith, was the Grand Marshall, while the Taoiseach, who is the country's first openly gay head of Government, travelled near the front of the parade.

Addressing the crowd in Smithfield, Mr Varadkar said: "I pledge as Taoiseach to use my office, for as long as I hold it, to advance the cause of LGBT rights, to press for marriage equality across Ireland, to speak up for LGBT rights around the world where they are under attack, and to push for the implementation of the sexual health strategy here at home at a time when it is more important than ever.

"I don't think my election as Taoiseach actually made history, it just reflected it, reflected the enormous changes that had already occurred in our country. 

"So, I don't think that I have changed things for you; I think people like you have changed things for me," said Mr Varadkar.

Elsewhere, Madrid is gearing up to be the world capital of gay pride, bringing together a colourful mixture of commercialism and all-night partying.

Under the motto Viva la Vida, Madrid World Pride is expected to welcome two million visitors during its 11-day run.

The city's famously gay Chueca neighborhood will serve as World Pride's centre, hosting many events, performances and parties, but the entire city will take part in the festivities.

Madrid officials have already installed a number of same-sex couple and gender neutral traffic lights across the city, which will remain in place even after World Pride is over

Istanbul Pride march banned for 'safety concerns' 

Turkish authorities said that an annual Pride march in Istanbul's Taksim Square would be banned due to "safety concerns", defying the calls of organisers.

Activists had called for the march for 5pm local time tomorrow but the city governor's office said that Taksim was not an official rallying ground.

"There will be no permission for a demonstration or a march on the said date considering the safety of tourists in the area... and public order," it said in a statement.

Authorities also urged citizens to ignore calls to participate in the parade and abide by the security forces' warning.

Last year, organisers were denied permission to march with the city on the edge over bombings blamed on the so-called Islamic State group and Kurdish militants, sparking anger from gay rights activists.

Riot police fired tear gas and rubber bullets to disperse protesters who defied the ban.

This year, the march coincides with the first day of the Islamic feast of Eid al-Fitr, and far-right groups have warned on social media against the parade.

Thousands took part in previous Istanbul pride marches, which were among the most significant LGBTQ events in the mainly-Muslim region.