"The Sri Lankan authorities must demonstrate generosity towards the Tamil population and grant Tamils autonomy and create a state that includes everyone," he said.
"The conflict is not resolved even if the battle has been won."
Sri Lanka's Tamil Tigers on Sunday admitted defeat in their decades-old battle for an independent ethnic homeland, with the remnants of their rebel army encircled by advancing government forces.
Norway helped broker a ceasefire in February 2002, which in practice came to an end in October 2006 when peace negotiations broke down.
Colombo stripped Norway of its role as broker of the island's moribund peace process in April following an attack by Tamil demonstrators on its embassy in Oslo.
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