Maputo - Mozambique police confirmed on Tuesday that 13 bodies had been found in the restive centre of the country where security forces have clashed with rebels from the Renamo group in recent months.The bodies were reported by local journalists last week while investigating allegations of a separate mass grave containing 120 corpses in the same area."The 13 bodies were buried on Saturday near the place where they were found," Armando Mude, police spokesperson for Manica province, told AFP."Due to their advanced state of decomposition, it was not possible to determine whether the bodies had bullet marks or not." The victims appeared to have been killed more than 45 days ago, he said. Human Rights Watch last week called for a "credible and transparent" investigation into the reported mass grave of 120 bodies.According to some farmers, villagers were killed by government troops who are battling the Renamo insurgents.Renamo fought a 16-year war against the Frelimo-led government that ended in 1992 before it became the largest opposition party.The Mozambican Human Rights League (LDH) on Tuesday called for a United Nations-led investigation into the alleged killings.At least 83 summary executions have been reported since the start of the year, LDH president Alice Mabota told reporters in Maputo."It is time that the authorities officially acknowledge that the clashes between security forces and Renamo armed men are not isolated... but that we are facing a civil war," she said.Renamo rejected the results of 2014 elections, which were won by Frelimo, the movement that led the country to independence from Portugal in 1975 and has ruled ever since.