Minister without portfolio Natwar Singh has hand-delivered his resignation letter at the residence of Prime Minister Manmohan Singh who has now left Moscow for Delhi, a copy of which was faxed to his hotel room in Moscow, sources said Wednesday.

• Volcker Report

Natwar Singh late Tuesday night hand-delivered a letter of resignation at 7 Race Course Road, the prime minister's residence in New Delhi, the sources said.

The letter was then faxed to the hotel room in Moscow where the prime minister was staying.

But at that time, he was at the banquet hosted in his honour by Russian President Vladimir Putin.

Dr Singh saw the letter only after reaching his hotel room, the sources said.

While announcing his decision to quit the Cabinet Tuesday night,  Natwar Singh had declined to answer whether he has sent his resignation to the prime minister.