SYDNEY (AFP) - A former sailor was jailed on Monday for more than three years after overpowering a guard and stealing a cache of weapons from an Australian navy vessel.

Matthew Evans, 26, was sentenced in the Darwin Supreme Court after donning camouflage clothing and a balaclava to raid his old ship, HMAS Bathurst, in the northern city in November last year.

The court heard Evans went aboard and overpowered a duty sailor, threatening him with a knife and tying him up.

Justice Judith Kelly said it appeared Evans, who pleaded guilty, felt pressured by a motorcycle gang to steal the weapons, including pistols and pump-action shotguns.

The dramatic raid prompted Australia's navy chief Vice Admiral Ray Griggs to order an investigation into security on all naval ships and bases.

Darwin is a vital navy port and the centre from which Australia conducts border control operations, with about 600 naval personnel in the area, many working at sea in border protection.