NEW DELHI (REUTERS) - India has asked Britain to extradite billionaire jeweller Nirav Modi, one of the main accused in the US$2 billion (S$2.74 billion) loan fraud at state-run Punjab National Bank (PNB).

Modi's whereabouts have been unknown since PNB in January said that two jewellery groups headed by Modi and his uncle, Mehul Choksi, defrauded the bank for years by raising foreign credit using fake guarantees.

The international police agency Interpol last month issued a request to find and arrest Modi.

But on Thursday (Aug 2), India's Foreign Affairs Ministry told Parliament it had sent an extradition request for Modi to Britain. It did not specify how it knew Modi was there.

Modi and Choksi have denied wrongdoing. Lawyers for both could not be immediately reached for comment on Friday.

The PNB fraud, dubbed as biggest in India's banking history, exposed shortcomings in the management of PNB and undermined confidence in India's state-run banking sector, which controls over two-thirds of the nation's bank assets.