/ Updated  / Source: Reuters

ISTANBUL (Reuters) - Three suspected Islamic State militants were arrested in Istanbul late on Tuesday after a tip-off they had planned an attack on a transgender march, Dogan News Agency said.

The suspects - one Turkish national and two from Russia's volatile Dagestan - were ordered held in custody pending formal charges by an Istanbul court, the agency added. There was no immediate comment from authorities.

People wawe rainbow flags as Turkish anti-riot police officers fire rubber bullets to disperse demonstrators gathered for a rally staged by the LGBT community on Istiklal avenue in Istanbul on June 19, 2016. Turkish riot police fired rubber bullets and tear gas to break up a rally staged by the LGBT community in Istanbul on June 19 in defiance of a ban. Several hundred police surrounded the main Taksim Square -- where all demonstrations have been banned since 2013 -- to prevent the "Trans Pride" event taking place during Ramadan. / AFP / GURCAN OZTURK (Photo credit should read GURCAN OZTURK/AFP/Getty Images)AFP/Getty Images

The reported arrests came after police late last week confiscated suicide vests during raids in two Istanbul suburbs. Officers said they had acted on intelligence reports the Sunni hardline group was plotting to attack the "Trans Pride" rally on June 19.

Authorities banned that march, citing security concerns and riot police fired tear gas and rubber pellets to disperse around 50 people who turned up.

Turkish police charge demonstrators who gathered for the march.Emrah Gurel / AP

Istanbul's governor has also banned a gay pride march scheduled for this coming Sunday, but campaigners say they will press on with the parade.

Dogan cited counter-terrorism police as saying the three suspects had traveled to war zones under Islamic State rule but did not specify where.

Islamic State has increasingly targeted NATO member Turkey, bordering Iraq and Syria where the group has seized large swathes of territory.

The group has been blamed for two suicide bombings in Istanbul this year and has carried out targeted killings in the southern cities of Gaziantep and Sanliurfa, both hubs for Syrian activists trying to document the war.

Istanbul has held gay pride parades since 2003, attracting tens of thousands of marchers, but last year's was broken up by police. Unlike many other predominately Muslim countries, homosexuality is not a crime in Turkey, but hostility toward gay people remains widespread.

A trans beauty queen participates in the annual Gay Pride March in Istanbul on June 29, 2014. Turkey is the only majority Muslim country where gay pride gatherings can take place. Photo by Jodi Hilton/NurPhoto (Photo by Jodi Hilton/NurPhoto) (Photo by NurPhoto/Corbis via Getty Images)Jodi Hilton / Corbis via Getty Images

Dagestan borders Chechnya, where Moscow fought two wars against Islamist separatists before regaining control of the region. A patchwork of ethnicities and languages, it has become a hub of militant Islam in the North Caucasus, and some militant groups have sworn allegiance to Islamic State.

(Reporting by Humeyra Pamuk; Editing by Ayla Jean Yackley and Andrew Heavens)