KANO, Nigeria (AFP) - Post-poll unrest in Nigeria has killed more than 200 people, a rights group said Wednesday, as the Muslim opposition candidate who lost alleged rigging but said he did not instigate the riots. Aid workers rushed to help nearly 40,000 displaced, many of whom had taken refuge in military and police barracks, while victims being treated in hospitals spoke of being hacked with machetes and beaten with clubs. Authorities say many were killed in the violence, which saw corpses burnt beyond recognition and bodies reportedly thrown into wells, but have refused to give a toll, saying it could spark reprisals and would be inaccurate. A well-known Nigerian civil rights group based in the northern city of Kaduna put the toll at more than 200 across the north. "In the whole region, from reports reaching Civil Rights Congress, the death toll is over 200," Shehu Sani, head of the organisation, told AFP. The numbers were compiled through his organisation's staff and associates. He added that more than 1,000 people had been arrested in the city of Kaduna alone, where a 24-hour curfew had earlier gone into effect. There were reports of fresh clashes in an area of the state of Kaduna overnight, with a community leader telling local radio "the killing was unbelievable and the destruction is colossal." One government official, explaining authorities' reluctance to release an overall death toll since the vote on Saturday, said, "I wouldn't like to use the term massacre... some places it was terrible." Curfews and military patrols appeared to have brought an uneasy calm to most areas Wednesday as many who fled slept in the open under trees at military and police barracks. The Red Cross said it had counted around 410 people wounded in the violence that began sporadically in the country's mainly Muslim north before spreading to some 14 states on Monday. It has also said there were many dead but has declined to give a number. Victims being treated at the main hospital in the northern city of Kano spoke of being attacked with machetes or clubs. One man said he was pulled out of his corner shop by dozens of youths, who looted and burnt his business. "Somebody used his machete to hit me on the forehead the first time, and the second time I tried to use my hand to protect my head and I sustained a big cut," 42-year-old Rotimi Ajayi said, bandages on his head and arm. The number of displaced had increased to 39,700, Red Cross disaster management coordinator Umar Abdul Mairiga told AFP.