Getting Spectrum Scan Error code 15007 on select query on redshift external table

I have created a external table in redshift spectrum.Upon running the select * from table_name, i am getting following error

SQL Error [XX000]: ERROR: Spectrum Scan Error
  Detail: 
  -----------------------------------------------
  error:  Spectrum Scan Error
  code:      15007
  context:   Forbidden: HTTP response error code: 403 Message: AccessDenied Access Denied

Please let me know what can be issue. I am able to do aws s3 ls and aws s3 cp command on same s3 location.

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