Blasts and gunfire at Sikh temple in Afghan capital
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While the number of bombings has dropped across the country since the Taliban seized power in August, several fatal attacks have rocked the country in recent months.
Interior ministry spokesman Abdul Nafi Takor said a grenade blast wounded two members of the Sikh community.
Minutes later a car bomb detonated in the area but caused no casualties, he added.
Singh, who was close to the scene, said the number of casualties could rise.
"Generally at that time in the morning we have several Sikh devotees who come to offer prayers at the gurdwara," he said.
The number of Sikhs living in Afghanistan has dwindled to around 200 compared to about half a million in the 1970s.
The jihadist group Islamic State claimed responsibility for that attack, which forced many Sikhs to leave the country even before the Taliban returned to power.
IS has a history of targeting Afghan Sikhs, Hindus and other members of minority communities -- including Muslim Shiites and Sufis.
A string of bombings hit the country during the Muslim holy month of Ramadan, which ended in Afghanistan on April 30, some of them claimed by IS.
The deadliest was in the northern city of Kunduz, where a bomb targeting Sufi worshippers tore through a mosque killing at least 36 people.
IS is a Sunni Islamist group, like the Taliban, but the two are bitter rivals.
The Taliban have pursued an Afghanistan free from foreign forces, whereas IS wants an Islamic caliphate stretching from Turkey to Pakistan and beyond.
Taliban officials insist their forces have defeated IS, but analysts say the jihadist group remains a key security challenge.