According to the United Nations, more than 120 people have died or been injured in the recent attacks in the Afghan capital Kabul.
The UN's Afghanistan mission (Unama) on Sunday called for more security for minorities so that they could celebrate religious ceremonies without further attacks.
On Sunday, according to local media reports, a third attack in three days hit a bus in a Shia-majority part of Kabul.
The terrorist militia "Islamic State" (IS) had already claimed responsibility for two previous bomb attacks on Friday and Saturday in another Shiite neighborhood.
The Taliban government did not comment.
The IS fighters are Sunnis and harbor a deadly hatred of all Shiites.
After the Sunnis, the Shiites represent the second largest religious current within Islam.
In Afghanistan, the Shiites are a minority.
They are currently preparing for Ashura Day, which commemorates the martyrdom of Imam Hussein, grandson of the Prophet Mohammed.
IS has been making attacks in Afghanistan since 2015 and is also fighting the ruling Taliban, who are also Sunnis.