The governor of a southern Afghanistan district that has become a key focus of U.S. military efforts to root out the Taliban was killed Tuesday in a bombing, Afghan and U.S. officials said. Also Tuesday, four NATO troops were killed in eastern and southern Afghanistan, raising the toll of one of the deadliest months for U.S.-led international forces in the nearly nine-year war. Abdul Jabar, chief of Arghandab district in the southern province of Kandahar, was returning home from work at 4:30 p.m. with his 17-year-old son and two bodyguards when a car bomb detonated next to his car, Arghandab Police Chief Zamaray Khan said. The son and one of bodyguard were also killed. 'The district chief was a very honest man,' Khan said. 'He had no personal enemies.' Khan said authorities suspect that the Taliban carried out the attack. 'They are here, and they are the only people who can do it,' he said. The Taliban has assassinated numerous government employees in southern Afghanistan, hindering U.S. efforts to bolster the presence of the government in Kandahar and surrounding districts. 'I don't think it's a coincidence that there have been attacks on government officials,' said Ben Rowswell, chief of the Canadian-led provincial reconstruction team in Kandahar. 'That's what you would expect from an insurgency that feels threatened by efforts to connect the people to their government.' Last week, a suicide bomber killed more than 50 people celebrating the wedding of a police officer in Arghandab. Western officials say it has been hard to recruit bureaucrats and police officers in Kandahar and other provinces where the central government has historically had a weak presence, because southern Afghanistan remains volatile and civil servants earn modest wages. Building up the local government is the cornerstone of an embattled NATO campaign to secure Kandahar, the country's second-largest city and the heartland of the Taliban. At least 44 NATO troops have been killed in Afghanistan his month. Tuesday's casualties included two British troops killed in separate shootings in the restive southern province of Helmand, according to the British military. A Polish service member was killed in a rocket attack on a base in Ghazni province, in eastern Afghanistan. An American service member was killed in eastern Afghanistan, military officials said. The spike in casualties comes as the U.S. military is deploying an additional 30,000 troops to Afghanistan amid rising violence. The Taliban has responded by stepping up attacks against NATO troops and allied Afghan officials. 'This is a tough loss,' Brig. Gen. Frederick Hodges, one of the top U.S. commanders in southern Afghanistan, said of Jabar's death. 'We knew the enemy was going to fight back because of the dramatic improvements that have taken place in Arghandab.' Gen. Stanley McChrystal, the top U.S. commander in Afghanistan, condemned the assassination. 'This attack shows the insurgents cannot offer a better alternative for peace and security,' McChrystal said in a statement. 'Their actions will only increase the suffering of those who seek a better future for Afghanistan.' _ Special correspondent Javed Hamdard in Kabul contributed to this report. 