Dec 10 (Reuters) - Russia has sent a planeload of humanitarian aid to Sri Lanka after the island nation was struck by Cyclone Ditwah in late November, Russia's RIA news agency reported early on Wednesday, citing Shobini Gunasekera, Colombo's ambassador to Moscow.

"A plane carrying 35 tonnes of humanitarian aid has already departed for Sri Lanka," Gunasekera told the news agency, adding that it was expected to arrive on Wednesday.

Ditwah, which was Sri Lanka's deadliest natural disaster since the devastating 2004 tsunami, killed 635 people and affected about 10% of the population. It damaged critical infrastructure and key crops such as rice and tea. Local officials warn that recovery costs could reach $7 billion.

(Reporting by Maria Tsvetkova; Editing by Paul Simao)