Islamic State claimed responsibility for a suicide attack on a crowded Shi'ite mosque in Kabul on Monday that killed more than 30 people and wounded dozens in its third major attack on minority Shi'ites in the Afghan capital since July.

Officials said the attacker entered the Baqir-ul-Olum mosque shortly after midday as worshippers gathered for Arbaeen, a Shi'ite ritual marking the end of a 40-day mourning period for the 7th century death of Imam Hussein, grandson of the Prophet Mohammad.

A statement in Arabic from Islamic State's Amaq news agency said one of its fighters had targeted the mosque.

Bloody sectarian rivalry between Sunni and Shi'ite Muslims has been relatively rare in Afghanistan, a majority Sunni country, but the attack underlines the deadly new dimension that growing ethnic tension could bring to its decades-long conflict.

Fraidoon Obaidi, chief of the Kabul police Criminal Investigation Department, said at least 27 people were killed and 35 wounded, while the United Nations said at least 32 had been killed and more than 50 wounded, including many children. It described the attack as "an atrocity".

"I saw people screaming and covered in blood," one survivor told Afghanistan's Ariana Television, adding that around 40 dead and 80 wounded had been taken from the building before rescue services arrived at the scene.

Another witness said he had helped carry 30-35 bodies from the mosque.

Protesters in Jerusalem have hung a gay pride flag on the office building of the city's chief rabbi, also drawing a rainbow on the sidewalk outside. It came after the religious leader said "homosexuality is an abomination" and "is punishable by death."

The chief rabbi's comments have been condemned by members of Israel's LGBT community and its supporters, with representatives of the Yerushalmim Movement - a group aimed at making Jerusalem a more pluralistic and inclusive city - demonstrating outside the offices of the Jerusalem Rabbinate on Sunday, along with other activists.

The protest was met with a counter-demonstration from United Jerusalem, whose members hit the streets to "defend the honor of the Torah and the honor of the rabbi," the Jerusalem Post reported.

At least two people have filed complaints with police over Amar's remarks, calling them incitement to bigotry, the Jewish Telegraphic Agency reported.

The head of Hebrew University's Meretz branch, Gilad Bar-on, has called for Amar to retract his statements.

"The blood-soaked statements of Rabbi Amar are unacceptable to us," Bar-on told Israel's Channel 2. "As the people who are paying his wages we demand that Rabbi Amar take it back."

His comments were also slammed by members of the Knesset and the Jerusalem City Council, many of whom supported Amar in his election to the post.

Several Knesset members wrote in a letter that Amar is "exploiting his position" as a public figure, accusing him of incitement.