Brothers Hadi and Awad al-Motleq and their accomplices Mufarraj and Ali al-Yami were found to have smuggled "a large quantity of hashish" into the kingdom, the ministry said in a statement carried by the official SPA news agency.
The beheadings raise to 32 the number of executions announced in Saudi Arabia so far this year, according to an AFP tally.
Last year, there were 78 executions in Saudi Arabia and the UN High Commissioner for Human Rights denounced a "sharp increase in the use of capital punishment".