Iraqi and U.S. military forces will ramp up security ahead of landmark provincial elections set for January 31 when up to 15 million Iraqis could go to the polls, officials said on Thursday.

Extensive security precautions at 42,000 polling stations aim to deter potential attackers and attempts to undermine the electoral process before and after the ballot, U.S. military spokesman Major General David Perkins said.

He told a press briefing in Baghdad that with the election preparations well under way he wanted to see a "multi-week-long process" that would help "legitimize the election process."

Perkins said that even after polling day there existed the possibility that some "malign elements" would try to thwart the process or interfere in the election outcome.

Iraq's Independent High Election Commission, with the help of the United Nations, is holding elections on January 31 in 14 of Iraq's 18 provinces -- the first vote in the country since 2005.

Iraqi and U.S. forces have especially focused on Diyala and Nineveh provinces, widely considered the country's most dangerous despite what the U.S. military says were sharp falls in the number of attacks in 2008 compared with 2007.

Brigadier General Ali Zouin al-Jubooria of the interior ministry's Election Security Committee said candidates in areas such as Mosul, capital of Nineveh province, would be offered police protection after recent killings of politicians.

"We've coordinated with candidates ... We are working on this and trying to resolve it," he said.

On December 31 unidentified gunmen shot Mowaffaq al-Hamdani, a candidate for Mosul, and on January 3 a member of the Kurdish Communist Party was killed by unknown assailants in Kirkuk.

With more than 400 political groups and 14,660 candidates bidding for election, security is expected to prove immensely complicated, officials said.

They refused to detail how many troops would be mobilised for the poll, however, citing security reasons.