A suicide bomber struck a bath house in a southern Afghan town as men gathered to wash up before Friday prayers, killing 17 people, a provincial official said.
The Taliban claimed responsibility for an attack they said targeted the deputy of an influential border patrol commander.
The attack came the same day NATO announced that three of its service members were killed in roadside bombings, underscoring the continuing threat the Taliban pose, despite a stepped-up coalition offensive.
The midday bombing killed 16 civilians and a police inspector in Spin Boldak near the Pakistani border, about 70 miles east of the provincial capital of Kandahar, said the governor's spokesman, Zalmay Ayubi. An additional 23 people were wounded, and officials said many of them were transported to Pakistan for treatment.
The condition of the commander was not known, Ayubi added.
A Taliban spokesman in the south, Qari Yousaf Ahmadi, said the attack targeted the second-in-command of the border patrol in the area. Officials have not identified the dead inspector as the border patrol deputy.
President Hamid Karzai, whose government has been battling the Taliban while trying to bring them to the negotiating table, called the bombing a "brutal" and un-Islamic act.
"Those behind this attack should know once again that the blood of the Muslim people has been spilled. It will not have any other result," Karzai said in a statement released by his office.
Continuing instability
The blast reflected the continuing instability in Afghanistan, particularly in the Taliban's traditional southern stronghold, scene of some of the fiercest fighting of a war approaching the start of its 10th year.
NATO has bolstered its forces in the south, but the insurgents have been able to stand their ground there while expanding their operations to other parts of Afghanistan once considered relatively safe.
The proximity of Friday's attack site to the Pakistani border also hinted at the tensions between Afghanistan and Pakistan.
The Taliban leadership is believed to be based in the Pakistani city of Quetta, 60 miles east of the Afghan-Pakistan border. Afghan officials have said repeatedly that allowing the insurgents to operate from within Pakistan is a threat to both countries.
The latest NATO deaths raised to nine the number of coalition forces killed this year and marked a grim start to 2011 for the forces. Last year, 702 NATO service members were killed, the deadliest year for the international force in Afghanistan.
NATO, which has roughly 140,000 troops in the country, has struggled to quell the insurgency. Coalition officials estimate Taliban's numbers at 25,000 — roughly unchanged despite the international force's stepped-up offensive against insurgent leaders and rank-and-file fighters. The U.S. said this week it would send an additional 1,400 combat Marines to Afghanistan.
The intensified effort is critical for NATO. U.S. President Barack Obama plans to begin withdrawing troops from Afghanistan in July and NATO combat troops are scheduled to pull out of the country by 2014, handing over full security operations to their Afghan counterparts.