Istanbul Governor Vasip Sahin said in a written statement on Friday: "During demonstrations across Istanbul, five policemen and 18 demonstrators were injured."
He said judicial proceedings against demonstrators who were detained were continuing.
He added: "Most demonstrators ignored illegal calls and celebrated the day in peace.
"More than 20,000 policemen worked to secure peace during the demonstrations in Istanbul."
Sahin thanked Istanbulites who he said responded to the May Day celebrations with "common sense".
He said some "marginal" groups had sought to disrupt public peace and security under the pretext of May 1st celebrations, and tried to enter Taksim Square with "explosive substances".
The statement continued: "Police seized two stun grenades, one gun, 54 Molotov cocktails, five firework launchers, six slingshots, six masks and a radio."
Taksim -- a major interchange on Istanbul`s European side and of symbolic importance for unions and leftists -- has been ruled out-of-bounds by the Turkish authorities in recent years.
Labor Day demonstrations in 1977 in Istanbul`s Taksim Square led to the deaths of 34 people and wounding of 136 in what became known as Bloody May 1.
The square was closed to demonstrations on Labor Day between 1977 and 2010.
Union activists have been barred from marching to the public square since 2013.
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