Pakistan police confirmed the explosion that ripped through a religious procession in Khanpur killing at least 18 people was caused by a bomb.

At first, police said the explosion was caused by faulty high-voltage electrical distribution cable but later said it was a remote-controlled bomb planted near an electricity distribution location.

Police near the explosion reported confusion as dust settled over the crowd, which initially turned on the officers as they tried to help the injured.

The explosion went off as mourners came out of a mosque, a report by the Pakistan newspaper Dawn said.

The bomb appeared to have been planted in the path of the procession near a utility pole ahead of time, District Police Chief Sohail Chatta said.

"There was a loud explosion a few yards from the procession and we all scrambled to get away," Imran Iqbal, one of the members of the procession, said.

"Debris was everywhere and a cloud of dust engulfed us. Many people died on the spot."

A police officer said the crowd of mourners started throwing rocks at police after the blast and officers had to use tear gas to control the crowd.

Members of the Shiite population were celebrating Chehelom, the 40th day of mourning. The observance commemorates the martyrdom of Hussein bin Ali, the grandson of the Prophet Mohammed and who Shiites say is the legitimate successor to the Mohammed.

Around 20 percent of Pakistan's population is Shiite and 70 percent is Sunni.

The explosion in Khanpur comes after another fatal explosion on the weekend, in Dera Ismail Khan, a Shiite-majority city in north central Pakistan. Dera Ismail Khan is in Khyber-Pakhtunkhwa province, around 200 miles west of Lahore.

The attack on a police station left four bombers, three civilians and a police officer dead, witnesses and other sources said.

The News International reported eight other people, including seven police officers were wounded in the attack.

"Four suicide bombers wearing jackets filled with explosives and carrying hand grenades and automatic rifles entered the compound of the [District Police Officer] offices but were immediately engaged by (police)," Syed Itiaz Shah, deputy inspector general for the district police, told the Pakistani newspaper.

One of the suspected attackers was captured but authorities haven't released details of the attackers' affiliations, religious or otherwise.

The city is close to Pakistan's Tribal Agency areas on the border with Afghanistan. Its Shiite and Sunni populations have suffered at the hands of many suicide bombers in the past several years. Many have religious connections but authorities also suspect Taliban is responsible for some of the blasts.

In August 2008 a suicide bomber targeting Shiites set off an explosive device in a hospital waiting room, killing 32 people, including seven police officers. Twenty of the dead were members of one family. Police said they suspected a Taliban bomber.

More than 30 people attending the funeral of a local Shiite man were killed when a suicide bomber attacked in February 2009.