UPDATE 6-Bomb kills 37 on last day of Pakistan vote campaign

(Adds U.S. comment)

By Zeeshan Haider

ISLAMABAD, Feb 16 (Reuters) - A suicide car bomb outside a Pakistani election candidate's office killed 37 people in the violent northwest on Saturday, the last day of campaigning for an election meant to complete a transition to civilian rule.

Separately, police in the south of the country said they had foiled another attack planned for polling day on Monday.

Campaigning for the elections to a new parliament and provincial assemblies has been overshadowed by security fears, especially since former Prime Minister Benazir Bhutto was killed in a gun and suicide bomb attack on Dec. 27. Opposition politicians have also complained of vote rigging.

The poll could spell trouble for President Pervez Musharraf, a key U.S. ally who stepped down as army chief in November, if voters elect a parliament hostile to him.

Voting was postponed from Jan. 8 after Bhutto's assassination, which raised fears about the nuclear-armed country's stability.

Saturday's bomb attack took place in the town of Parachinar in the Kurram region on the Afghan border which has seen bloody sectarian clashes between majority Sunni Muslim militants and minority Shi'ites in recent months.

Supporters of a candidate backed by Bhutto's Pakistan People's Party (PPP) were going into his office after a rally.