Since January 2016 there have been 51 incidents resulting in 273 deaths and 577 wounded -- nearly double the number of casualties for the previous seven years, the UN Assistance Mission in Afghanistan (UNAMA) said in a report.
The incidents involve attacks against mosques and worshippers as well as targeted killings, abductions and intimidation of religious leaders.
"The unprincipled brutality of such attacks is reflected in the appalling human cost," UNAMA said.
The Sunni extremist group Islamic State has claimed most of the attacks on Shiite worshippers as it seeks to stir up sectarian violence in the country.
Also Read
The UNAMA report comes ahead of Shiite ceremonies for Arbaeen this week, which marks the end of a 40-day mourning period after Ashura.
Such religious events have been targeted by militants in the past because prayer halls are likely to be packed with worshippers, maximising the number of casualties.
Last year's Arbaeen commemorations in the Afghan capital were marred by a bloody attack on a Shiite mosque that killed or wounded scores of people.
"Attacks against Shi'a (Shiite) Muslims and their places of worship may be expected to continue -- or increase -- if action is not taken," the UN said.
In the most recent attack on October 20 a suicide bomber pretending to be a worshipper walked into a Shiite mosque in Kabul and blew himself up, killing 56 people and wounding 55 others.
In September, ahead of Muharram -- the mourning period for the seventh-century killing of the grandson of the Prophet Mohammed -- the government announced a plan to arm more than 400 civilians to help defend Shiite mosques.
Disclaimer: No Business Standard Journalist was involved in creation of this content