A homicide bomber on foot entered a government office and blew himself up Monday in the volatile south, killing eight people, including four policemen, officials said.

The district police chief was among the seven people wounded in the attack on the Nad Ali district center in Helmand province, said district chief Mehbob Khan.

Four civilians were among the dead, Khan said. The seven wounded included policemen and civilians.

Helmand has been the front line in the battle between the Taliban and international forces in recent months and has seen some of the bloodiest fighting in the past two years. It is also the largest opium-producing area in the world.

More than 4,300 people — mostly militants — have died in insurgency-related violence this year, according to an Associated Press tally of figures from Western and Afghan officials.

Among the latest casualties are 120 insurgents who were killed over the past 20 days in a joint U.S. coalition and Afghan operation in central Ghazni province, the Interior Ministry said Monday.

Last month, the Afghan army had dropped leaflets warning of impending military action in Ghazni — the province where 23 South Koreans were kidnapped in July — though the army said the operation had been long-planned and was not linked to the kidnappings.

"In the past 20 days of operations in Ghazni province, 120 enemies of the peace and stability of Afghanistan have been killed. Five commanders of the enemy have been captured," said Interior Ministry spokesman Zemerai Bashary. It was not possible to confirm the figures independently.

Officials have reported at least four Taliban commanders involved in the July 19 abduction of the South Koreans have been killed in Afghan security operations this month, but it is not clear if they were included in the death toll announced Monday.

The South Koreans were kidnapped while driving by bus from Kabul to the southern city of Kandahar.

Two of the hostages were slain soon after the kidnapping. Two women were released during Taliban negotiations with South Korea, and the remaining 19 were freed late last month.

Meanwhile, NATO and Afghan army troops came under fire Sunday morning in Surobi district, about 25 miles east of Kabul, and called in airstrikes, killing at least one suspected insurgent, said Maj. Charles Anthony, spokesman for NATO's International Security Assistance Force.

One weapons cache was destroyed, he said. There were no reports of NATO, Afghan army or civilian casualties.

Surobi police chief Gen. Yardil Nizami said the bombardment destroyed one house in the village of Gazbala, killing two men and wounding two others.

Nizami did not know if the casualties — all from the same family — were militants or civilians, but noted many villagers in the area support insurgents. He added that many Arab, Chechen and Taliban insurgents had recently been in the area.

The Interior Ministry has sent a delegation to investigate the incident, Bashary said.