Patna, Nov 11 (IANS): Policemen in plainclothes have been deployed and those in uniform alerted to keep a close watch for Maoists who try to exchange their old currency notes with new ones, police officials said on Friday.

A senior police official here said police have been alerted in Maoist-affected districts of Gaya, Aurangabad, Arwal, Jehanabad, Muzaffarpur and Sitamarhi to swoop down on Maoists who arrive at banks or post offices to exchange or deposit demonetised Rs 500 and Rs 1,000 currency notes they have collected through 'levy'= and extortion.

The Centre had, from November 8 midnight, demonetised these high-denomination notes in an effort to fight black money and terror funding. 

Police officials in Gaya and Aurangabad, two of the worst Maoist-hit districts bordering Jharkhand, said intelligence networks have been alerted to keep a track of activities of the Maoists and their supporters. 

"We will not allow them to exchange old notes and will arrest them," a police official said.

"Maoists have collected crores of rupees through levy and keep cash with them for their activities and distribution among their cadres and followers."

Police said cash is also used by the Maoists to purchase firearms and ammunition, besides for investing in real estate business and other sectors.

'Levy' is a big business for the Maoists as contractors, traders, businessmen and government officials fear them and pay up with or without threats.