At least 17 Pakistani soldiers have been killed after a car packed with explosives exploded next to a pair of fuel tankers at an army check post in the country's northwest, officials say.
The offcials, who are unnamed because they were not authorised to speak to the media, said dozens were also injured in the attack which occurred on Saturday night in the North Waziristan tribal area.
North Waziristan is the main sanctuary for Taliban and al-Qaeda fighters along Pakistan's restive border with Afghanistan.
The army confirmed the death toll in a text message sent to reporters.
The blast set the fuel tankers on fire, destroying two residential army barracks, said intelligence officials.
Janan Dawar, who lives about 14km away from the attack site in the town of Mir Ali, said he heard a huge explosion and saw flames leap into the air.
Among the 34 people wounded three were civilians. Most of the 17 soldiers who were killed were working for a wing of the army that is building roads in North Waziristan.
Winning hearts and minds
The US has funded much of the road construction in the area in an attempt to win hearts and minds of the locals.
The Pakistani army has tens of thousands of soldiers based in North Waziristan but has resisted US pressure to launch an offensive against anti-government fighters in the area.
The US has been pushing for an operation because Afghan Taliban fighters use North Waziristan as a base to launch cross-border attacks against US troops in Afghanistan.
The Pakistani military says it cannot launch an offensive because its forces are spread too thin fighting domestic Taliban fighters who are waging war against the government.
But Pakistani troops have fought for years against rebels 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 Pakistan.