A 60-year-old man who allegedly was wielding an axe and throwing small explosive devices from his gopher has been arrested in the city this morning.

About 2.30am, the man allegedly rode past a group of units in Sturt St on his motorised 'gopher style' scooter and let off an explosive device at the front door of one of the apartments, police say.

He also allegedly threatened the victim with a small axe before riding away.

There was no substantial damage caused to the units.

Police searched the area, and located the man on his Gopher in Whitmore Square.

The 60-year-old Adelaide man was arrested and charged with arson and aggravated assault, and has been refused bail.