A Taliban suicide bomber blew himself up Thursday inside a mosque in southern Afghanistan, killing a deputy provincial governor and five other worshippers in the latest assassination of a senior official in President Hamid Karzai's government, officials said. The attack came hours after a suicide car bomber struck an army bus in the capital, Kabul, killing a civilian and wounding four other people. The assaults suggest the militants could continue their bombing campaign this year after 2007, when they launched more than 140 suicide missions - the highest number since the ouster of the Taliban in the US-led invasion of 2001. The bomber in the southern province of Helmand struck a mosque in the provincial capital Lashkar Gah and killed six people including the deputy governor, Pir Mohammad, said provincial police chief Mohammad Hussein Andiwal. The blast also wounded 18 people including two children and damaged the mosque's walls, Andiwal said. Zabiullah Mujahid, a spokesman for the Taliban, said the attack was carried out by an Afghan named Qudratullah from the eastern province of Paktia. His claim could not be independently verified. Karzai called the attacks "brutal and terrorist acts." "(These attacks) are un-Islamic acts of enemies of Afghanistan, aimed at innocent civilians and Muslim people," the president said in a statement. Mohammad had served as a deputy governor of Helmand for the past five years. He had two wives and 11 children, said Sher Mohammad Akhunzada, a former provincial governor. Andiwal said Mohammad had just arrived from a meeting at the Helmand governor's nearby compound. "After finishing his meeting, the deputy governor walked to the mosque for prayer," Andiwal said. "As they were praying, the bomber detonated his explosives." The mosque's prayer leader was among those killed, he said. Haji Ikramullah, who was on his way to pray when the blast occurred, said he saw dead bodies inside and wounded people shrieking in pain. Helmand is the center of world's opium and heroin production and a scene of intense clashes between militants and British, US and Afghan government forces. The Taliban often attack Afghan officials as part of their effort to weaken the control of Karzai's US-backed government. Provincial officials are key components in the government's attempt to extend its control and provide services in lawless areas. The militants have moved away from direct confrontations with foreign troops, which inflict heavy casualties on them. Instead, the militants increasingly resort to suicide and roadside bombings. Most victims have been civilians. Last year, suicide bombers in the eastern province of Khost tried three times to kill Gov. Arsallah Jamal. He survived, but a number of his guards were killed. A suicide bomber killed Paktia's governor, Abdul Hakim Taniwal, outside his home in September 2006. Another killed six people at Taniwal's funeral the next day. The mosque blast Thursday came hours after a suicide car bomber targeted an Afghan army bus in Kabul, killing one civilian and wounding four other people, officials said. The blast shattered the bus windows and damaged a passing taxi, said police officer Jan Agha. A soldier was among the wounded, he said. A series of attacks last year targeted buses carrying Afghan security forces, an important element of US efforts to beat back the insurgency gripping the country's south and east. In two incidents alone 65 people, mostly soldiers, were killed. More than 6,500 people - mostly insurgents - died in the violence last year, according to an Associated Press count of figures provided by local and international officials. On Wednesday militants beheaded four road construction workers and dumped their bodies on the roadside in the eastern province of Nuristan, said deputy provincial police chief Mohammad Daoud Nadim. The four were kidnapped 10 days ago while working on a road project, Nadim said. Meanwhile in Kabul, hundreds of people demanded the release of an Afghan journalist who was sentenced to death last week after he was found guilty of insulting Islam. The demonstrators from the small, secular Solidarity Party rallied in front of the United Nations office in support of 23-year old Sayed Parwez Kaambakhsh, who was sentenced by a three-judge panel in the northern city of Mazar-i-Sharif for distributing to journalism students a report he had printed off the Internet. The article asked why Islam lets men have four wives but does not allow women to have multiple husbands. Kaambakhsh has appealed his conviction. International human rights groups have condemned the sentence. The upper house of Afghanistan's parliament welcomed the ruling and criticized "international interference" in the matter.