MAZAR-I-SHARIF, Afghanistan (Reuters) - A suicide bomber killed some 50 people and wounded 50 on Tuesday in an attack on a group of visiting Afghan parliamentarians in northern Afghanistan, the director of the local hospital said.

The suicide attack, in the northern town of Baghlan, is the worst in Afghanistan's history.

"The bodies of 90 people have been brought to the hospital so far and 50 people have been wounded," Baghlan hospital director Dr. Khalilullah told Reuters.

He said there might well still be dead and wounded on the streets who had yet to be brought to the hospital.

Details of the suicide bombing were still unclear.

Provincial governor Mohammad Alam Ishaaqzai said 50 civilians had been killed in the blast and five parliamentarians, including opposition spokesman Mostafa Kazemi, were among the dead. Many schoolchildren had also been killed, he said.

A deputy agriculture minister and prominent woman parliamentarian Shukria Barakzai were among the wounded.

Baghlan's intelligence chief, Abdurrahman Sayedkhail, said the number of casualties was so high it was impossible to give an accurate number for now.

"I saw bodies lying in the streets and some of the people were stealing the weapons of the dead soldiers. Children are screaming for help. It's like a nightmare," said local resident Mohammad Rahim who said the blast had killed his two cousins, both schoolgirls.

The attack took place as the delegation was visiting a sugar factory in the industrial part of the town of Baghlan. Large crowds of residents and schoolchildren crowded the visiting parliamentarians who were on an economic fact-finding mission.

Northern Afghanistan has escaped much of the violence which has wracked other parts of the country since the Taliban relaunched their insurgency against the Kabul government and the 50,000 foreign troops in the country.

The hardline Islamist Taliban have killed more than 200 people in more than 130 suicide attacks so far this year in a campaign of violence aimed at convincing Afghans their government and its Western backers are incapable of providing security.