By Salman Rao
RAWALPINDI, Pakistan (Reuters) - A suicide bomber killed 13 people at Shi'ite processions in the city where Pakistan's army is headquartered on Wednesday night, highlighting the country's security challenges a day before it hosts leaders from Egypt, Iran and other developing nations.
Local television stations said 13 people were killed but police put the death toll at eight. Twenty-five people were wounded, including children.
The blast ripped a hole in the walls of a Shi'ite mosque in the city of Rawalpindi, near the capital Islamabad. Body parts were scattered at the scene.
Hundreds of worshippers, beating their heads and chests, kept marching, even though other explosive devices were found at the site.
There was no immediate claim of responsibility for the attack which occurred hours after two bomb blasts killed at least three people near a gathering of Shi'ites in Pakistan's commercial hub and biggest city Karachi.
Hardline Sunni militant groups linked to al Qaeda have in recent months stepped up attacks against Pakistan's minority Shi'ites, whom they regard as non-Muslims.
Pakistan's military, one of the world's biggest, has failed to break the back of a persistent insurgency despite launching several offensives against their strongholds in the northwest near the border with Afghanistan.
Pakistan hosts a summit of eight developing nations on Thursday. Pakistan, Iran, Egypt, Turkey, Indonesia, Malaysia, Nigeria and Bangladesh are expected to discuss ways of boosting trade and investment at an event which Islamabad hopes will improve its standing. Some presidents have already arrived.
Pakistani Interior Minister Rehman Malik said the attacks were designed to hurt Pakistan's image and create the impression that its U.S.-backed government is incapable of establishing stability.
"We are trying to build relationships, get investment in Pakistan and these groups are trying to derail the process," he told Reuters.
Pakistani authorities are bracing for what could be a bloody weekend, the climax of the Shi'ite mourning month of Muharram. Radical Sunni groups have staged high-profile attacks on that occasion in the past.
Thousands of security personnel are expected to be deployed in a bid to avoid attacks. About 50,000 people are expected to march through the streets of Islamabad on Saturday.
Muharram marks the anniversary of the Battle of Karbala where the grandson of the Prophet Mohammad and his family members were killed.
Earlier on Wednesday, a bomb blast killed three soldiers and two civilians in the Pakistani city of Quetta, security officials said.
The bomb, attached to a motorcycle, exploded near a security vehicle escorting school children, they said. Sixteen people were wounded. A Reuters reporter saw the bodies of three soldiers under the vehicle as it burned.
There was no immediate claim of responsibility for the attack in Baluchistan, Pakistan's biggest but poorest province which borders Afghanistan and Iran, and where several militant groups are active.
(Additional reporting by Mehreen Zahra-Malik and Mubasher Bukhari in ISLAMABAD; Writing by Michael Georgy; Editing by Louise Ireland)