The two suspects in a Southland crime have fled to Dunedin, where they've been arrested.

Police apprehended a 15 year old girl and 20 year old man in Mosgiel this morning.

Last night the girl allegedly assaulted a 57 year old woman she lives with, threatening her with a knife at their Invercargill home.

She then reportedly stole the older woman's car and drove north with her male associate.

The couple evaded police at Waihola, but the car was stopped by road spikes at Allanton about 2am.

The suspects fled on foot and were apprehended in Wingatui Road about five hours later.

Police have yet to lay charges.