MAZAR-I-SHARIF, Afghanistan - A suicide attack on a parliamentary delegation killed at least 50 people in northern Afghanistan on Tuesday, a provincial official said, in the worst such blast in the country's history.

Five members of the Afghan parliament were among the dead and the toll was expected to rise among the delegates and schoolchildren who were among the victims.

"We have recorded 50 people dead so far, but there are still bodies on the streets we have not counted and some of the dead have already been taken away by their relatives," Baghlan provincial security chief Abdurrahman Sayedkhail told Reuters.

The attack took place as the parliamentary delegation was visiting a sugar factory in the town of Baghlan. Large crowds greeted the parliamentarians, who were on an economic fact-finding mission.

The bomber was on foot and blew himself up as the delegates entered the factory, Sayedkhail said. Many of the dead were schoolchildren who had lined up to greet them.

"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. He said the blast had killed his two cousins, both schoolgirls.

Opposition spokesman and former Commerce Minister Mostafa Kazemi and four other parliamentary deputies were among the dead.

"The bomber got very close to the delegation as they were being greeted. He got very close to Mostafa Kazemi and blew himself up," Sayedkhail said. "He was carrying a massive amount of explosives."

Before the attack, the hardline Islamist Taliban had killed more than 200 people in more than 130 suicide attacks this year in their campaign to overthrow the pro-Western Afghan government and eject the 50,000 foreign troops from the country.

But northern Afghanistan has escaped much of the violence which has wracked other parts of the country since the Taliban relaunched their insurgency two years ago.

The director of the hospital in Baghlan initially said 90 people had been killed in the attack, but later put the toll at between 60 and 90.

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

"The president has condemned this in the strongest possible terms," said presidential spokesman Humayun Hamidzada.

"The president has also ordered the Ministry of Defence to send all the necessary help to treat the injured ... and also ordered the Ministry of Interior to conduct an investigation right away."