A suicide bomber has killed at least 27 people in a suicide attack inside a Shia Muslim mosque in the Afghan capital, Kabul, police say.
Another 35 were wounded in the blast at the Baqir ul Olum mosque.
The attacker was on foot and blew himself up among crowds inside the building, officials said.
There was no immediate claim of responsibility but it comes amid mounting sectarian attacks on Afghanistan's Shia community.
This latest bombing took place during a service to commemorate the death of Imam Hussein, the Prophet Muhammad's grandson and Shia martyr.
According to eyewitnesses, the service was almost over when the bomb was detonated on the first floor.
"I was inside the mosque and the Mullah was reading the prayer," Ewaz Ali, 50 who suffered minor injuries, told the Associated Press news agency.
"Suddenly a huge explosion happened, then everywhere was dark."
Local reports suggest there are children among the dead.
Afghan government chief executive Abdullah Abdullah took to Twitter to urge the country not to fall victim to "enemy plots that divide us by titles".
"This attack targeted innocent civilians - including children - in a holy place." he said. "It is a war crime and an act against Islam & humanity."
Shia, who make up about 15% of the population of Afghanistan, have been spared the levels of sectarian violence seen by Pakistan and Iraq.
But Shia groups have been targeted at least three times in recent months, including in a gun attack on a shrine in Kabul in October and a blast during a Shia protest march in July, which left 80 dead.
They have all been claimed by so-called Islamic State, the Sunni Muslim militant group.
Taliban militants, who are seeking to reimpose Islamic rule in Afghanistan, were quick to distance themselves from Monday's attack.
"We condemn this blast," Taliban spokesman Zabihullah Mujahid told the BBC. "This a