Istanbul, May 1 (DHA) - Confederation of Progressive Trade Unions (DİSK) leader Kani Beko and Confederation of Public Laborer's Unions Lami Özgen arrived Beşiktaş, to start the May Dah march towards Taksim, the main square of the city under police blockade. Members of the Union of Chambers of Turkish Engineers and Architects (TMMOB) and the Turkish Medical Association (TTB) are also expected to join the two confederation's members. Istanbul’s iconic Taksim Square and surrounding districts, including Besiktas, are on lockdown by more than 20 thousand police officers and iron crush barriers to prevent celebrations of May Day. Authorities in Istanbul have tightened security ahead of the national holiday, with iron barricades erected in the city center. Taksim Square has symbolic meaning for the Turkish left, as over 30 people were killed in 1977 when suspected nationalists opened fire on May Day participants from what is now the Marmara Hotel. VIDEO STREAM ------------------- - Arrival of Kani Beko and friends - Kani Beko chants the May Day slogan - Statement - General and detail views