Can banks recover amount from nrega amount credited to sb a/

Procedural law is not a legal dispute.

Contact branch manager of concerned Bank.

There is no specific law protecting the NREGA amount credited to SB account from being recovered by Banks. The amount in SB is open to General Lien Bankers enjoy to recover their dues. Therefore, bank can recover the amount available in your SB account to the extent of overdues in your loan account.

Only if there were no conditions attached to such credits by Central Government.  In certain cases of such credit the authority that remits the amount, that this amount should not be attached for any other dues to the bank.  Make a complaint to RBI online first to get their clarification.

NREGA amounts credited to the beneficiary's account are not protected from attachment etc. The bank can in the exercise of bankers' lien recover its dues from the amount. 

There is no such protection. Had it been so, the earnings from NREGA would have credited into an exclusive SB account.