The bomb blast went off outside a sugar factory in the northern province of Baghlan as the lawmakers were about to go inside. The blast struck school children, Afghan elders and government officials who had gathered to greet the visiting delegation of 18 lawmakers from the lower house, officials said.
The Ministry of Interior said at least 28 people were killed in the blast, but a doctor at Baghlan's main hospital, Dr. Mohammad Yousuf Fayez, said dozens of dead bodies may also have been left at the blast site and collected by families, meaning they wouldn't have been counted officially. Earlier, a high-ranking government official said 64 people had died.
At least 42 school children were among 81 people wounded, Fayez said.
"The children were standing on both sides of the street, and were shaking the hands of the officials, then suddenly the explosion happened," Fayez said.
Shukria Barakzai, a lawmaker, said 18 of the 249 lower house parliamentarians had traveled to Baghlan province, and that 13 were dead or "in danger."
Baghlan lies about 150 kilometers (95 miles) north of Kabul.
President Hamid Karzai's office confirmed the deaths of five parliamentarians.
"This heinous act of terrorism is against Islam and humanity and I condemn it in the strongest possible terms," Karzai said in a statement. "It is the work of the enemies of peace and security in Afghanistan."
The attack is among the deadliest in Afghanistan since the 2001 U.S.-led invasion. Taliban bombers have killed regional governors in the past, but never have militants killed so many high-ranking officials in one attack.
A U.S. military spokesman said the blast was the same as those often carried out by the Taliban. Lt. Col. David Accetta , who condemned "this kind of terrorist and criminal attack," said he had no information indicating al-Qaida was behind the blast.
The northern Afghan region where the blast happened is known for tensions between the mainly ethnic Tajik government leadership and remnants of the militant group Hezb-i-Islami, whose fugitive leader Gulbuddin Hekmatyar, an ethnic Pashtun, is allied to Osama bin Laden and al-Qaida but has denied organizational links.
Kamin Khan, a police official, said people "everywhere" were dead and wounded, including police, children, lawmakers and officials from the Department of Agriculture.
Among the at least five lawmakers killed was Sayed Mustafa Kazimi, a former Afghan commerce minister and a powerful member of the Northern Alliance, said the lawmaker's secretary, Ahmadi, who gave only one name. Kazimi also served as the spokesman of the largest opposition group in Afghanistan, the National Front.
Interior Ministry spokesman Zemeri Bashary confirmed the deaths of 28 people. He said the lawmakers were part of parliament's economic commission.
He blamed the attack on the "enemy of Afghanistan, the enemy of the people of Afghanistan," a term commonly used here to refer to Taliban militants but that could also include other terrorist groups like al-Qaida.
This year has been the deadliest in Afghanistan since the fall of the Taliban. More than 5,700 people have been killed in insurgency-related violence, according to an Associated Press count based on figures from Western and Afghan officials.
The choice of the city of Helsinki is not incidental as the capital of Finland had hosted US-Soviet negotiations on the limitation of nuclear stockpiles in 1969