The Cabinet Division issued a gazette notification in this regard, describing Qaboos bin Said as a true friend of Bangladesh.
The national flag will be flown at half-mast at all government and private offices, including educational institutes, in the country and Bangladesh missions abroad.
Besides, special prayers will be offered at mosques and other places of worship for the salvation of the Sultan’s departed soul, it added.
Sultan Qaboos bin Said was Middle-East’s longest-ruling monarch who seized power in a 1970 palace coup and pulled his Arabian sultanate into modernity while carefully balancing diplomatic ties between adversaries Iran and the US.
The sultan was believed to have been in poor health and travelled to Belgium for what the court described as a medical checkup last month.
The state-run Oman News Agency announced his death late Friday on its official Twitter handle.