CARACAS/PUERTO ORDAZ, Venezuela (Reuters) - Venezuela s opposition refused on Wednesday to swear in newly-elected governors before a pro-government legislative superbody it deems unconstitutional, as a small protest broke out in southern Bolivar state over fraud allegations. The pro-government electoral council announced in the middle of the night that the ruling socialists had won the Bolivar governorship, meaning President Nicolas Maduro s government took 18 of 23 states in Sunday s vote. Polls had put the opposition far ahead, and anti-Maduro politicians have alleged a litany of dirty tricks including switching electoral centers to dangerous areas at the eleventh hour and gross abuse of state resources.  However, they have failed to give evidence of ballot-tampering, and some opposition candidates have conceded they lost due to high abstention in their demoralized ranks.  Still, the disparate opposition coalition said its five winning candidates would not be sworn in by the controversial legislative superbody known as the Constituent Assembly.   The governors-elect will only be sworn in as established in the constitution and the laws of the Republic,  the Democratic Unity coalition said in a statement on Wednesday. Leftist Maduro has previously said that governors not sworn in by the pro-government legislative body will not be allowed to take their posts in a country reeling from widespread food and medicine shortages, a collapsing currency and soaring inflation.  He described Venezuela s electoral system as the world s most secure and slammed U.S. President Donald Trump and other foreign leaders who questioned the veracity of the vote. Bolivar became a flashpoint after the electoral council briefly showed the opposition winning on its web site Sunday night before proclaiming the Socialist Party candidate as winner in the early hours of Wednesday.  Opposition candidate Andres Velasquez accused the electoral council of invalidating some ballots cast for him.  Pockets of his supporters protested outside the electoral board s offices in state capital Ciudad Bolivar, with some clashes breaking out on Monday and Tuesday. Some 50 people rallied on Wednesday, though the protest quickly fizzled.   I am going to demonstrate to the world that this electoral process is fraudulent,  Velasquez told local radio in Bolivar, home to many of Venezuela s gold and diamond mines. However, nationwide protest like those that rocked Venezuela for four months earlier this year are not expected, given fatigue and disappointment among demonstrators. The perennially divided opposition is in disarray after Sunday s election, with some leaders calling fraud and others conceding defeat, often in uncoordinated press statements.  Sunday s election has left the socialists more confident of winning a presidential vote expected in late 2018.  