PARACHINAR, Pakistan -- A bomb blast tore through a political rally held by an Islamist party in northwest Pakistan Monday, in an attack claimed by the Pakistani Taliban that killed 16 people and underscored an increase in violence ahead of the May 11 vote.

The explosion, at a rally held in the village of Sewak in the northwest Kurram tribal area, was the latest attack on candidates, political offices and election-related events as the vote approaches. Much of the violence is believed to have been carried out by the Taliban against three liberal and secular parties. But Monday's blast targeted a gathering of the Jamiat Ulema-e-Islam party which generally has a more favourable relationship with the militant group.

The bomb, which was apparently planted near the main stage of the rally, killed 16 and left 44 wounded, said Umar Khan, a doctor at the nearby Sada hospital where many of the wounded were initially taken.

Two party leaders who were speaking at the event escaped unharmed.

About 2,500 people had gathered at a local religious school to hear the candidates speak, said one man who was in the crowd, Sabir Gul. The massive explosion came just as one of the candidates ended his speech and was leaving the stage, he said.

One of the candidates, Ainuddin Shakir, told a local television station that the bomb appeared to have been detonated by remote control.

Another resident, Mohammad Jamil, attended the meeting with his brother and was in the dining hall eating when the explosion occurred. Political parties often give food to people at rallies who sometimes travel from nearby villages to hear candidates speak. Jamil said people attending the rally had been searched as they went into the gathering.

"There was a deafening sound which stunned me for a while but I quickly moved out of the dining hall," he said, describing a "hell-like" situation. "There were countless people bleeding and crying for help. My brother Khalil was among them."

The Jamiat Ulema-e-Islam party is considered supportive of the Afghan Taliban's fight against the United States and its allies in neighbouring Afghanistan. It's also sympathetic to the Pakistani Taliban, which have been fighting Pakistani troops and would like to establish a hardline Islamic government in Pakistan. The group's leaders have generally opposed the Pakistani military's operations against militants in the tribal region and instead called for negotiating with the militants.

The Taliban have claimed responsibility in recent weeks for a string of attacks against secular Pakistani parties that have in general supported military intervention against the militants in the tribal regions.

Claiming responsibility for Monday's bombing, Pakistani Taliban spokesman Ahsanullah Ahsan said the attack was aimed at a candidate who had appeared at the rally -- Munir Khan Orakzai. Ahsan said Orakzai was targeted because he supported operations against militants in the tribal areas when he was previously an independent parliamentarian.

The historic vote, scheduled for this Saturday, will be the first time a democratically elected civilian government completes its term and hands over power to another. But the ongoing attacks against candidates, their supporters and political offices has cast a shadow over the momentous occasion, and may deter many people from going to the polls.

There is also concern that the attacks could benefit the parties that take a softer line toward the militants, because they are able to campaign more freely ahead of the vote. But the Taliban has also condemned democracy as a whole, meaning that any political party taking part in the elections could be considered fair game by the militant group. Militants have called on people in many areas to stay away from the polls on election day.

Some militants in Pakistan have shown a willingness to target anyone connected to the U.S.-backed government in Pakistan, even those, like the head of Jamiat Ulema-e-Islam, who have called for negotiating with the Taliban in Pakistan or have been outspoken supporters of the Taliban in Afghanistan.

In 2011, a suicide bomber struck a convoy in which the party's head, Maulana Fazlur Rehman, was travelling through northwestern Pakistan, killing 12 people.

Monday's blast, said Raza Rumi from the Islamabad-based Jinnah Institute, showed that even groups such as Rehman's are not immune to the election-related violence.

"Any political force or religious group which adheres to the constitution of Pakistan .... is under attack from the militants. It's as simple as that," he said.

The violence is multi-faceted and reflects the various militant problems facing the Pakistani government and military.

Most of the violence has come in the northwest, where Pakistan has been battling militants intent on overthrowing the government, and in the southern city of Karachi, where Taliban fighters have gained a foothold. Numerous attacks have also hit candidates in the southwestern Baluchistan province, where Baluch rebels are battling Pakistani troops.

On Sunday in Baluchistan, two gunmen attacked a convoy of an independent candidate and killed two of his police guards.

On Friday, in Karachi, gunmen killed an anti-Taliban election candidate along with his 6-year-old son and a political activist.