A senior Tripura police official said Tuesday: 'Security forces in the northeast India are on the alert for fake currency notes being circulated - strongly believed to be the handiwork of the Inter-Services Intelligence (ISI) of Pakistan.'

He said that the matter came up for serious discussion at the recent high-level meetings of the region's police chiefs held in Guwahati and New Delhi.

'ISI was pumping fake currency notes into the region (to destabilize the economy) along with guns, ammunition and other contraband items, often with the help of various insurgent groups,' the official added.

Fake currency in Rs.100, Rs.500 and Rs.1,000 denominations are mostly in circulation in the northeast region.

Nationalised banks and various other financial institutions in northeast India have taken a series of measures, including installation of fake note detection machines to identify fake currency.