The Papua New Guinea electoral commission has announced that fresh elections are to be held in six of the southern highlands electorates as soon as possible.
103 of the 109 seats have now MPs and parliament is due to meet on Monday to elect a new prime minister.
The commissioner, Reuben Kaiulo, has now accepted the outcome of the elections in Enga province and also approved the results on three southern highlands electorates.
And Mr Kaiulo says fresh elections for the outstanding six seats can only be held if there is guaranteed protection for election workers and the public.
The poll was affected by ballot papers being destroyed and by intimidation.
Meanwhile, police have issued a call-out for troops to help in the security clampdown in the capital, Port Moresby, from Saturday.
This is part of a security operation ahead of Monday's planned vote.
The security arrangements include a ban on MPs carrying firearms in parliament.
Private security of MPs in hotels will be replaced by police and troops.
Papua New Guinea's first prime minister, opposition politician Sir Michael Somare, has been asked to form the next government after his party won the most seats.