Members of this parliamentary party staged similar rallies in several other Croatian cities and towns today.
The head of the HSP Zagreb branch, Stjepan Sterc, said that it was the European Union that stood behind Tadic's visit to Vukovar because of its attempts to promote the Serbian president as a regional leader.
The HSP also criticised Tadic for planning to visit Paulin Dvor on the same day as Vukovar, regarding it as an attempt to apportion the blame for war crimes.
Paulin Dvor is a community near Osijek where on 11 and 12 December 1991 Croatian troops killed 19 civilians, including 18 ethnic Serbs and one Hungarian.
Vukovar is the symbol of Croatia's resistance to the Serbian military aggression during the 1991-1995 Homeland War and the site of one of the worst atrocities committed in Europe after the Second World War.
Vukovar was peacefully reintegrated into Croatia's legal and constitutional system in early 1998.