PESHAWAR (AFP) - A suicide bomber rammed a water tanker bomb at a Pakistani military check post late Saturday, killing six soldiers in the notorious tribal district of North Waziristan, officials said.

More than 20 other people, mostly soldiers, were wounded in the bombing near Miranshah, the main town in North Waziristan, they said.

"Half of the check post building has been destroyed in the blast," said a security official in the northwestern city of Peshawar, warning that the casualty figure could rise.

"It was a suicide attack. The bomber used a water tanker, he rammed it into the outer wall of the building," the official said.

A security official in Miranshah said the dead included an army officer.

Pakistani troops have fought for years against homegrown insurgents in the tribal belt on the Afghan border.

There are fears that rampant insecurity could prove a major challenge for historic general elections on May 11, which should mark the first democratic transition of power between two civilian governments in Pakistani history.