The UN in Sri Lanka says many people - including children - have been killed by shells landing on a hospital in rebel-held territory in the north-east. UN spokesman Gordon Weiss told the BBC the shells had hit a crowded pediatric unit. It is not clear who fired them. Earlier the Red Cross said two people had been killed on a separate strike on the same hospital. It is situated in an enclave held by the Tamil Tiger rebels and home to tens of thousands of civilians.