(ANSA) - BELGRADE, FEB 11 - Serbian President Aleksandar Vucic has called for a large gathering of his supporters on next Saturday, Serbia's National Day. This demonstration, he stated in an Instagram post, will take place in Sremska Mitrovica, a city 75 kilometres west of Belgrade, and a Declaration will be solemnly adopted there to confirm Vojvodina's full membership in Serbia. This is Vucic's response to the appeals that have emerged in recent weeks, on the sidelines of student protests, for a possible secession of Vojvodina, the northern region (capital Novi Sad) which is the richest and most developed in the country. (ANSA).