Rwanda on Sunday said there was no evidence a group of rebels who surrendered in neighbouring DR Congo are Rwandan citizens, and called for a joint verification of their nationalities. \"There is no evidence that they were Rwandan citizens,\" said Rwandan army spokesman, Brigadier-General Joseph Nzabamwita. The group -- comprising 29 people according to Kigali, 24 according to the U.N. -- are presented by the U.N. as having surrendered from the M23 rebels, a group formed by Congolese army mutineers fighting in the eastern Kivu regions. The group, who say they are Rwandan nationals according to the U.N., surrendered in May after deserting from the M23, an event seen as the first indication the rebels had received support from Rwanda. The rebels said at the time of their surrender they were recruited in Rwanda and sent to DR Congo to join the M23, whose rebellion has caused a spike in tensions between the two countries. UN peacekeepers took the group to the border Saturday to hand them over to Rwandan authorities, who refused to accept them. \"They wanted media publicity for propaganda purposes,\" Nzabamwita added, calling the \"sudden repatriation\" of the group \"highly irregular.\" \"We have sent an official communication to our counterparts in the Congolese army for a joint verification exercise,\" he added. The U.N. said Rwanda did take custody of seven rebels from the Democratic Forces for the Liberation of Rwanda (FDLR), a Rwandan Hutu militia group based in eastern DR Congo that Kigali says includes members who participated in Rwanda\'s 1994 genocide. U.N. experts in June said there was \"overwhelming evidence\" that senior Rwandan army officers had backed M23 with fighters, weapons and supplies. But Rwanda has denied involvement and in turn accuses the DR Congo of renewing cooperation with the FDLR, which opposes Rwandan President Paul Kagame.