TOKYO (AFP) - A 25-year-old mother whose two young children starved to death surrounded by rubbish after she locked them in her apartment has been sentenced to 30 years in jail in Japan, reports said on Wednesday.

Single mother Sanae Nakamura regularly left her daughter, 3, and one-year-old son, in the apartment in western Osaka while she spent the night at her boyfriend's house, reports said.

She had begin leaving them alone in March 2010, the Asahi Shimbun said, adding that sometime in early June that year she stopped coming home. But when she did eventually return later that month the two tots were dead, the paper said.

Nakamura was convicted of murder by Japan's lower courts and sentenced to 30 years at earlier hearings, which found she had known that leaving the children without sufficient food would kill them.

The country's supreme court on Monday upheld the sentence, the Asahi and Kyodo News reported on Wednesday.