MIRANSHAH  – The death toll from Saturday night’s suicide attack on a security checkpost in North Waziristan’s Miramshah area reached 17, the military said.

There was no immediate claim of responsibility for the attack. North Waziristan is perhaps the most notorious of Pakistan's tribal districts on the Afghan border, a known stronghold of the Taliban and Al-Qaeda-linked operatives.

The deaths were a reminder of the serious security threat in the country, just hours before former military ruler Pervez Musharraf returned to Pakistan after more than four years in exile. "In last night's attack on a security forces' checkpost in North Waziristan, 17 security forces personnel embraced shahadat (martyrdom)," the military said.

Security officials explained the sudden increase in the death toll after it jumped from six by saying that many of the dead had been trapped under the rubble following the blast.

Another 10 soldiers were also wounded in the attack on a checkpost operated jointly by the regular army and the Frontier Corps paramilitary. 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 country’s history. A car packed with explosives had exploded next to a pair of fuel tankers at an army checkpost in North Waziristan, killing 17 soldiers and wounding dozens, officials said Sunday. Most of the security personnel killed belonged to the Tochi scouts who were deployed for the security of FWO officials.

The FWO is engaged in several development projects in the area. The blast set the fuel tankers on fire and destroyed two residential army barracks, said intelligence officials, speaking on condition of anonymity because they were not authorized to talk to the media. Janan Dawar, who lives about 14 kilometers away from the attack site in the town of Mir Ali, said he heard a huge explosion and saw flames leap into the air. The blast killed 17 soldiers and wounded 34, said the intelligence officials. Three civilians were also wounded.  The US has funded much of the road construction in the area in an attempt to win hearts and minds of the locals.The army confirmed the death toll in a text message sent to reporters.

The army has tens of thousands of soldiers based in North Waziristan but has resisted US pressure to launch an offensive against militants in the area. The US has been pushing for an operation because Afghan Taliban militants allegedly use North Waziristan as a base to ‘launch’ cross-border attacks against American troops in Afghanistan.

The military says it can't launch an offensive because its forces are spread too thin fighting militants who are waging war against the government.

But many analysts believe the Pakistan army is reluctant to cross Afghan militants with whom it has historical ties and could be useful allies in Afghanistan after most foreign forces withdraw at the end of 2014.

However, the area has become a greater problem for the Pakistani military because domestic Taliban militants have increasingly used it as a base of operations and conduct periodic attack against soldiers based in the area.