At least, four people were killed and four others wounded as a female suicide bomber blew herself up outside a hospital in a tribal area in North West Pakistan, officials said Saturday.

"At least four people were killed and four others were wounded in the blast outside the main gate of the hospital," Dr Mohammad Riaz, chief doctor at the government hospital told AFP.

The attack that killed security personnel and hospital worker and two civilians took place outside the District Headquarters Hospital in Khar town in Bajaur tribal district bordering Afghanistan.

Confirming the gender of the bomber, local administration official Abdul Haseebhe stated: "It was a female suicide bomber, about 18-20 years old, we have found her legs and head."

The injured were shifted to the hospital while authorities have started an investigation into the incident.

No group has claimed responsibility for the attack yet. However, Pakistan’s Taliban had vowed to increase attacks ahead of the general elections in May 2013.

Bajaur is part of the Pakistan’s Federally Administered Tribal Areas (FATA) in the country’s northwest region bordering Afghanistan, where the Taliban, Al-Qaeda and other militant groups have a strong presence. The Pakistani army has launched several offensives against the militants in the region since 2008, flushing out most of the militant leaders from the province.

More than 3,000 Pakistani security personnel have been killed in the anti-militant operations.

However, the militant groups have continued their attacks unabated, from across the border villages in Afghanistan.

Despite undertaking several counter-insurgency measures against the militants, Pakistan’s military has failed to reign in extremist groups backed by the Al-Qaeda and the Taliban, which has stepped up attacks in the wake of the May general elections.