Prime Minister Narendra Modi wrote to his Japanese counterpart Fumio Kishida expressing India's solidarity with Japan and its people affected by the devastating earthquake on January 1.

On Thursday, Modi wrote to Kishida that India values its relationship with Japan as a special strategic and global partner, and is ready to extend all possible assistance at this hour, sources said.

Around 90 people were killed when a 7.6 magnitude earthquake struck Japan's northernmost peninsula of Noto on Monday.

The prime minister conveyed to his Japanese counterpart that he is "deeply anguished and concerned" over the earthquake and expressed "deepest condolence" to the families of those killed in the quake, the sources said.

"I am deeply anguished and concerned to learn about the major earthquake that struck Japan on January 1," Modi said.

"I express my deepest condolences to the bereaved families of those who lost their lives. We stand in solidarity with Japan and its people affected by the disaster," a source quoted Modi as writing to the Japanese prime minister.

Japan's Kyodo news agency said on Friday that the death toll in the quake rose to 92 with over 240 people still missing.

It said authorities doubled the number of Self-Defence forces' personnel taking part in earthquake rescue operations to 4,600.

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