Three youths allegedly caught by police dumping a shotgun and two machetes following a series of armed hold-ups in Melbourne have been charged.

Three Dandenong North men - aged 18, 19 and 21 - have been charged with armed robbery and weapon offences.

The trio were arrested just before 5am on Thursday at Glen Waverley after alleged armed robberies at Narre Warren North and Mount Waverley earlier in the morning.

The men were allegedly spotted by officers disposing of the weapons in a garden bed before being arrested.