Mode of payment for invoice payment from foreign entity

Hi. My company is in Belgium. We don't have a branch in India. We are planning to hire some associates as contract staffing through a consultancy in India. In which currency the monthly invoice payment need to be made ? In INR or EUR ?. Will there be any tax implications for the Belgian company in India if they pay in INR ? Can they do wire transfer or Do they want to open any account in India to do this transaction ?