Most of the extra forces have been sent to improve security in the heavily forested Southern Highlands, where polls in six of the nine electorates were declared invalid after the 2002 election because of widespread intimidation and violence.
Mark Karambi, spokesman for the Electoral Commissioner, said that apparently missing names from the rolls were probably due to a "mix-up" of listings from one village to the next.
The 2002 violence was blamed on supporters of rival candidates in a country where tribal loyalties play a role in politics.
Michael Somare, the incumbent prime minister, is seeking re-election on his National Alliance Party ticket.
Nearly two thirds of the candidates in the polls are independents, and they have not joined into a single voice of opposition to Somare's party.
One of the main challengers to Somare, who has served three separate terms since Papua New Guinea's independence from Australia in 1975, is former treasurer Bart Philemon.
Philemon, who was fired by Somare last year, was widely credited with imposing some discipline on government spending after years of mismanagement.
Candidates in the highlands have vowed to disrupt this year's poll, claiming thousands of names have been wrongly dropped from the electoral roll.
About half of the 35 candidates contesting one of the province's parliamentary seats were seeking to delay the start of the poll claiming that, in some village districts, 75 per cent of names had been dropped from the electoral roll while in other areas 20 per cent more names were added.
Claims of vote rigging and corruption are difficult to verify in a country where campaigning often ignites simmering tensions between tribes.
Somare says this year's polling will be free and fair. Voting runs until July 10.