A prisoner swap between Georgia and South Ossetia has turned sour after the rebel region jailed two Georgian teenagers for explosives offences.Five South Ossetians were freed under an EU-sponsored deal and were welcomed by family and friends in the region’s capital Tskinvali. But the second part of the plan ran into problems as the two sides continue to argue more than a year after they fought a brief war. Hours after Tbilisi freed the five prisoners, South Ossetia put four young Georgians on trial for illegally entering the breakaway republic armed with grenades and other weapons. Two of them are aged 14, the others are aged 16 and 17. The youngest two were freed, but the elder pair’s 12-month prison terms were immediately denounced by Georgia. The EU supported calls for their release and said they may be pardoned soon. Police released video pictures they claim show how the four crossed into South Ossetia in early November carrying bags of explosives. It is not clear what they intended to do.