A suicide bomber struck a Sunni mosque Friday in northeastern Afghanistan, killing four people, just days after a deadly attack targeted Shiites in a rare sectarian attack in the capital.
An Islamic extremist group in Pakistan has claimed responsibility for the Kabul attack, raising already sharp tensions between the two neighboring countries.
Friday's bomber blew himself up about 2 p.m. outside a Sunni mosque in the Ghazi Abad district of Kunar province, a hotbed of the insurgency in the east where the U.S.-led military coalition has shifted its focus after working to rout the Taliban from their strongholds in the south. Insurgents regularly cross the porous border from Pakistan to conduct attacks in Afghanistan.
The blast occurred on the last day of Ashoura, a Shiite festival marking the seventh century death of Imam Hussein, the Prophet Muhammad's grandson, but most of the congregation is Sunni and the targets appeared to be police and government officials.
Those killed included the district police chief, his bodyguard, an employee of the Afghan intelligence service and a civilian, said Gen. Ewaz Mohammad Naziri, the provincial police chief. Five other people were wounded in the blast, he said.
"It was a brutal act against Afghan Muslims inside a mosque," he said. "They had gathered for prayers and he entered and blew himself up."
Mosques have frequently been attacked in Afghanistan and suicide bombings have become more common as insurgents shift tactics to destabilize the country and erode confidence in the government and security forces as U.S.-led forces prepare to withdraw by 2014.
The bombing against a Shiite shrine on Tuesday was different because it was aimed at Shiites gathered to commemorate Ashoura. At least 56 people were killed and more than 160 wounded in the first major sectarian attack in Afghanistan since the fall of the Taliban regime a decade ago.
More than 2,000 people converged under tight security in a field west of Kabul to mark the last day of Ashoura and voice opposition to militant and terrorist groups that they say have been given sanctuary in Pakistan. Enlarged photographs of the bombing victims were hung at the site.
Mohammed Mohaqeq, a Shiite leader in the Hazara ethnic minority, said the international community must help prevent militant groups based in Pakistan from attacking sites in Afghanistan. He also called for those responsible for Tuesday's deadly bombing to be prosecuted by the international courts.
Former Afghan President Sibghatullah Mojaddedi placed direct blame on the Pakistan intelligence service, the Inter-Services Intelligence agency, or ISI.
"Don't say it's foreign intervention, say it is Pakistan and the ISI. All of us know it," Mojaddedi said. "The ISI is recruiting terrorists, coming across the borders into Afghanistan and doing suicide bombings. God will get revenge."
A man claiming to be from Lashkar-e-Jhangvi al-Alami, a Pakistan-based splinter group of Lashkar-e-Jhangvi that has carried out attacks against Shiite Muslims in Pakistan, called various media outlets to claim responsibility for the Kabul bombing and a nearly simultaneous attack that killed four Shiites in the northern Afghan city of Mazar-e-Sharif.
But Pakistani military spokesman Gen. Athar Abbas has dismissed any suggestions that Lashkar-e-Jhangvi has links to the country's intelligence agencies.
Abdullah Abdullah, a top opposition leader, said Afghans must unite to fend off those trying to prevent Afghanistan from becoming a vibrant, independent nation. "The future of Afghanistan is at stake," he said.
Separately, in the south, a joint Afghan and NATO coalition force destroyed nine roadside bombs found while patrolling Friday in Maiwand district of Kandahar province, the coalition said. Another joint patrol in the same district uncovered nearly 1,550 pounds (700 kilograms) of marijuana seed, the coalition said.
Associated Press writer Deb Riechmann contributed to this report.