ISLAMABAD, Pakistan - Gunmen kidnapped the son of a former Pakistani prime minister Thursday at a campaign rally in southern Punjab province as violence continued to rise ahead of Saturday's national election, which some call the bloodiest in the country's history.

Hours after his youngest son, Ali Haider Gilani, was kidnapped and two others killed in the attack, former Premier Yousuf Raza Gilani urged supporters of their Pakistan People's Party to keep campaigning. The young Gilani is a candidate for the provincial assembly in the Multan district, where the attack occurred and where two of his brothers are running for seats in the parliament.

Their father, who served as prime minister for more than four years until forced to step down by the Supreme Court in a contempt case last year, criticized the temporary caretaker government for not providing sufficient security for candidates.

Islamist militants have waged bomb and gun attacks for the past month against the liberal People's Party and two secular coalition partners in the outgoing government.

The moderate forces in the country were not being provided with "the favorable environment to campaign and take part in elections," Yousuf Raza Gilani told reporters at his home in the central city of Multan, adding that his son's secretary and guard died in the attack.

He said he did not know who carried out the kidnapping. The Pakistani Taliban, which has asserted responsibility for previous attacks and has threatened to kill voters at the polls, said it was not behind the Multan incident, the Reuters news agency reported.

The gunmen grabbed Ali Haider Gilani after he left a building to meet with a few hundred supporters, according to local television newscasts.

Because of recent attacks, which since April have killed more than 110 people, the People's Party, the pro-U.S. Awami National Party and the Karachi-based Muttahida Qaumi Movement have been constrained in their campaigning.

Rather than holding large rallies, they have mostly relied on advertising, door-to-door politicking, and small meetings.