KABUL, March 26 (Reuters) - A would-be suicide bomber accidentally blew himself up on Thursday, killing six other militants as he was bidding them farewell to leave for his intended target, the Interior Ministry said.

"The terrorist was on his way to his destination and saying good-bye to his associates and then his suicide vest exploded," a statement from the ministry said.

Taliban-led attacks in Afghanistan have escalated in the past year with suicide and roadside bombings insurgents' weapons of choice.

The incident happened in Helmand province in southern Afghanistan where mainly British troops are struggling against a growing Taliban-led insurgency.

In a separate incident in Helmand, nine policemen were killed when Taliban insurgents attacked a police post in Nari Sarraj district, the Interior Ministry said.

Elsewhere, four Taliban insurgents were killed and seven policemen and two civilians wounded during a battle just outside Ghazni city, about 200 km (125 miles) southwest of the capital Kabul, a spokesman for the provincial governor said.

On Friday, Washington is set to unveil a review of its strategy in Afghanistan, which is expected to emphasise the need to expand Afghan security forces and strengthen the country's heavily aid-dependent economy. (Reporting by Golnar Motevalli; Editing by Valerie Lee)