Sweden's defence minister is to resign in the wake of weeks of allegations he knew about controversial plans for the Nordic state to help build a weapons plant for Saudi Arabia, the government said on Thursday.

Defence Minister Sten Tolgfors survived the initial reports in early March by public radio about plans for the weapons plant by saying he had not known of them. But reports of the details of the affair have continued to surface, increasing pressure on him.

He (Tolgfors) has resigned at his own request, said Roberta Alenius, spokeswoman for Prime Minister Fredrik Reinfeldt.

(Reporting by Johan Ahlander, writing by Patrick Lannin)