KABUL, Afghanistan (AP) — A suicide bomber struck a crowd of Shiite worshippers marking a holy day Tuesday in the Afghan capital as at least 20 people were killed in an unprecedented wave of violence against the minority Islamic sect in Afghanistan.

The Kabul attacker blew himself up in the midst of a crowd of men, women and children gathered outside the Abul Fazl shrine to commemorate the seventh century death of the Prophet Muhammad’s grandson Imam Hussein. Some men were beating themselves in mourning and food was being distributed.

A bomb strapped to a bicycle also exploded as a convoy of Afghan Shiites was driving down the road, shouting slogans for the festival known as Ashoura, in the northern city of Mazar-i-Sharif.

Sayed Kabir Amiri, an official in charge of Kabul hospitals, said at least 16 people killed and more than 100 were wounded in Kabul. At least four were killed and 21 wounded in the Mazar-i-Sharif attack, said Sakhi Kargar, a spokesman for the health ministry.

Religiously motivated attacks on Shiites are rare in Afghanistan although they are common in neighboring Pakistan. No group claimed responsibility for Tuesday’s blasts, reminiscent of the wave of sectarian attacks that shook Iraq during the height of the war there.