KABUL, Afghanistan — Dozens of schoolchildren and five teachers were among those killed in a suicide attack in northern Afghanistan earlier this week -- the country's deadliest since the fall of the Taliban -- the government said Friday.

The 59 schoolchildren had lined up to greet a group of lawmakers visiting a sugar factory in the northern province of Baghlan on Tuesday when a suicide bomber detonated explosives.

"The education minister has ordered that no children should be ever again be used in these sort of events," said Zahoor Afghan, an Education Ministry spokesman. He said the children ranged in age from 8 to 18.

In all, the explosion claimed the lives at least 75 people, including several parliamentarians, and wounded 96. It was the deadliest attack in the country since the toppling of Taliban regime from power in the 2001 U.S.-led invasion.

Afghan President Hamid Karzai declared three days of mourning Wednesday and ordered an investigation. No group has claimed responsibility, and the Taliban denied any involvement.

Also Friday, NATO and Afghan troops battled Taliban fighters near Gulistan district in western Farah province. The soldiers seized the district center, killing up to 20 suspected militants who overran it last week, said Gen. Abdul Rahman Sarjang, the provincial police chief.

On Thursday, U.S.-led coalition and Afghan troops surrounded a compound where militants had gathered near Tirin Kot, in Uruzgan province, sparking a clash which left seven suspected Taliban fighters dead, said Juma Gul Hamat, the provincial police chief. Four militants were detained, he said.

There were no casualties among coalition and Afghan forces, Hamat said.

In southern Zabul province, Taliban militants on motorbikes ambushed and killed Shahjoy's district chief and two bodyguards as they were shopping on Thursday, said Mohammad Rasool Khan, a district police chief.

Coalition and Afghan troops, meanwhile, came under fire from Taliban insurgents in southern Helmand province's Nahr Surk district on Wednesday, a coalition statement said.

"The combined force immediately engaged the Taliban fighters with small-arms fire and close air support, killing many of the insurgents before they fled the area," it said.

Violence in Afghanistan this year has been the deadliest since the Taliban's ouster. More than 5,700 people, mostly militants, have died so far this year in insurgency-related violence, according to an Associated Press count based on figures from Afghan and Western officials.

Separately, a British soldier was killed Friday in a vehicle accident in Afghanistan, the British Ministry of Defense said.