Are the foreigners required to register at police/immigration office on arrival if they are visiting Belarus for less than 5 days?
No. From GOV.UK:
Anyone staying for more than 5 working days in Belarus must register with the local police office (OVIR) in the district in which they are staying. Registration will normally be arranged by your hotel. If you are not staying in a hotel registration must be organised by your host. There are fines for not registering in time. If you arrive at the weekend, the earliest you will be able to register is Monday (but offices are only open until 1pm).
