A car bomb killed a district chief in eastern Afghanistan on Monday as he entered a provincial headquarters, but the governor escaped unhurt, officials said.

The attack in the heart of Jalalabad, the capital of Nangarhar province, happened during the morning rush hour as the chief of Lal Pur, a district of the province, drove into the provincial governor's compound.

This year has seen the bloodiest period in Afghanistan since the Taliban's removal in 2001, with the militants making a comeback despite the presence of almost 150,000 foreign troops.

Nangarhar Governor Gul Agha Sherzai, target of several attacks by the Taliban in the past, was inside the compound when the attack happened but was unharmed, his spokesman said.

It looks like the explosives were placed inside the district chief's car. We are still investigating. The district chief was killed and four others were wounded, Ahmad Zia Abdulzai said.

Earlier, an army official said the attack had been carried out by a suicide bomber.

Flames could be seen rising from the site of the blast and security forces had cordoned off several roads leading to the area in the city, which lies near the border with Pakistan.

The Taliban largely rely on bomb and suicide attacks in their campaign against the Afghan government and its foreign backers.

As the militants launch increasingly brazen attacks around Afghanistan, foreign troops have also stepped up operations, leading to heavy insurgent casualties and soaring international troop deaths.

CIVILIAN DEATHS

But ordinary Afghans have borne the brunt of the fighting, with thousands of civilians killed as they are caught up in the crossfire. Civilian deaths were up by 31 percent in the first six months of this year, according to a United Nations report.

On Monday, the NATO-led force said it had ordered a formal investigation into allegations its troops had killed civilians during a helicopter air strike in northern Baghlan province earlier this month.

The investigation was prompted by an initial assessment into the incident, NATO said, which found that rounds from the helicopters had fallen short, missing their target and hitting two buildings, which may have resulted in civilian casualties.

Last week, Afghan officials said eight civilians were killed in the raid, which was aimed at insurgents.

While most civilians are killed in insurgent attacks targeting Afghan and foreign troops, deaths of ordinary Afghans by international forces cause the most outrage among the population and have led to rifts between President Hamid Karzai and his Western backers.

Afghanistan is also preparing for a parliamentary election next month, viewed as a test of stability in the country that has seen violence rise to its highest levels in the nine-year war.

Poor security, particularly in Taliban strongholds in the south and east, already looms as the biggest challenge to the ballot, along with corruption and fraud.

On Sunday, five campaign workers for a candidate in next month's poll were killed by unknown gunmen. Four candidates have also been killed in recent weeks, drawing sharp criticism from the United Nations, which is assisting with the election.

(Writing by Sayed Salahuddin and Jonathon Burch; Editing by Alex Richardson)

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