ISTANBUL -- Transgender rights activists say they will go on with a march Sunday in Istanbul despite the governor's ban against it and police security precautions that could eventually be used against protesters.

The rights group Istanbul LGBTI, host of the 8th Trans Pride March, said on social media it won't recognize the ban. The march is to begin at 5 p.m. (1400 GMT) Sunday in central Taksim Square. The organization tweeted "all roads lead to Taksim."

The Istanbul governor's office banned the march late Saturday for the second year in a row. It said "marginal groups" on social media had called for the march and it was being banned to preserve public order and to keep participants and tourists safe.

The ban also said "very serious reactions have been raised by different segments of society," a reference to threats by conservative and ultranationalist groups against gay and transgender rights marches.

Istanbul police began closing multiple roads to traffic at noon Sunday as part of their security measures. Police buses, checkpoints and a water cannon were filmed near Taksim Square.

The U.S. consulate in Istanbul issued a security message warning U.S. citizens of possible "heavy police presence and counter demonstrations" and asking them to exercise caution Sunday. The message also said participating in the illegal gathering could lead to detention or worse under a state of emergency that Turkey imposed after last summer's failed coup.

Last week, the governor's office banned a march for LGBT rights for the third year. Police set up checkpoints to prevent participants from gathering and used tear gas and plastic bullets to disperse crowds. Forty-one people were detained.