ŠTÚROVO, Slovakia (Reuters) - The mainly ethnic Hungarian town of Štúrovo defied Slovak Prime Minister Vladimír Mečiar on Sunday by symbolically staging a referendum that he cancelled last month. Former President Michal Kováč had called the countrywide referendum on NATO membership and, more controversially, changing the method of selecting the president to a direct vote of the people from the current vote in parliament. Štúrovo is the only Slovak town to push through Kováč`s referendum and has therefore become a focal point in Slovakia`s seven-week-old constitutional crisis. The crisis is rooted in the failure of Mečiar`s government and the opposition to agree on a compromise presidential candidate in parliament and there is no mechanism for breaching the impasse. A referendum on changing the method of selecting the president to a direct vote of the people had been seen by Kováč and the opposition as the only way of breaking the deadlock. Most presidential powers are now in Mečiar`s hands. His first move on assuming the new powers was to cancel Kováč`s referendum. The Štúrovo town council went ahead with its own referendum, ignoring warnings from Mečiar of grave consequences if the town defied the central government`s will. Štúrovo Mayor Jan Oravec said voting, which was to end on Sunday night, was going peacefully and members of the town`s electoral commission said turnout looked to be strong. Sunday`s referendum was doubly sensitive because Štúrovo, which has 13,000 inhabitants, borders Hungary and is 70 percent populated by ethnic Hungarians, some of whom do not speak Slovak. The fiercely nationalist pro-government daily Slovenská Republika last week denounced the Štúrovo referendum as an attempt by Hungarian nationalists to subvert the Slovak state. It called on the government to mobilise state police and even the armed forces to prevent the referendum from taking place. Neither was to be seen in Štúrovo on Sunday. The Štúrovo town council says it has no nationalist aims. Mečiar`s government, threatened anyone cooperating with the referendum with legal action. Štúrovo`s referendum is purely symbolic although it has become a cause celebre among the country`s opposition and has attracted huge interest from Slovak and Hungarian media.