KANDAHAR, Afghanistan — Afghan troops backed by NATO attack helicopters battled Taliban fighters wearing suicide vests who launched an assault Friday in the heart of a major city in southern Afghanistan, witnesses and officials said.The gunbattle in Lashkar Gah, capital of Helmand province, occurred nearly two weeks after a similar assault in the Afghan capital of Kabul. The assaults appeared aimed at undermining confidence in the government and demonstrating that insurgents can attack even the most protected targets.Friday’s assault came one day after President Hamid Karzai announced plans for a national reconciliation program, offering militants jobs and homes in return for laying down their arms.Provincial officials said two attackers blew themselves up and one Afghan soldier was wounded in the fighting, which began about 10 a.m. when the insurgents opened fire from a building under construction near an army barracks.Taliban spokesman Qari Yousef Ahmadi claimed responsibility for Friday’s attack, saying the Taliban had dispatched a team of seven men armed with suicide vests and machine guns to attack the local branch of the U.N. mission in Afghanistan and a guesthouse used by government officials in the city.Ahmadi said 20 foreigners had been killed and wounded, but NATO said the Afghan troops backed by attack helicopters had contained the gunmen in a vacant, four-story building and no casualties were reported on the pro-government side.Sporadic fighting continued as Afghan troops searched for the other militants. Police officials said they believed five or six militants were holed up inside the building but at least two had blown themselves up.Daoud Ahmadi, a spokesman for the provincial government, said officials had received tips in recent days that the Taliban planned an attack on government buildings in Lashkar Gah.Afghan forces sent reinforcements to the area after insurgents hiding in the vacant building opened fire at a nearby army barracks on the western edge of the city, NATO said in a statement. Two rockets also slammed into a nearby area as the fighting began about 10 a.m., it said.Deputy provincial police chief Kamal Uddin said no civilian casualties had been reported and residents in the area were safe.The Taliban have attempted similar commando-style attacks in Kabul, most recently on Jan. 18 when seven gunmen and suicide bombers were killed after a five-hour assault. Five Afghan civilians and security forces also died in that fighting.The brazen daylight attacks by a handful of determined militants dramatize the vulnerability of urban areas and undermine public confidence in Karzai’s government and its U.S.-led allies — even as the United States and its international partners are rushing 37,000 reinforcements to join the eight-year war.Karzai said Thursday he would convene a peace jirga — or conference — to discuss proposals and would reach out to low-level Taliban and “our disenchanted brothers who are not part of al-Qaida or other terrorist networks.”He made the remark in London as he sought international support at a conference on Afghanistan for a plan to persuade Taliban fighters to disarm in exchange for jobs and homes.———Associated Press writer Amir Shah in Kabul contributed to this report.