Thousands of mourners gathered Friday in and near a Qatari mosque to bid farewell for the slain leader of Palestinian Islamist Hamas, Ismail Haniyeh, after he was killed in Tehran earlier this week, Qatari state television said.

The funeral service, which was also attended by Qatari and Arab officials, began at noon (0900 GMT) with a prayer at the Imam Abdul Wahhab Mosque, the largest state mosque in Qatar.

According to Hamas, Haniyeh’s body would then be buried in a cemetery in the city of Lusail, north of Doha.

Qatari state television, which is broadcasting live, reported the highest security precautions around the ceremony.

It added that the burial ceremony would therefore take place within the immediate family circle.

Haniyeh, and some of his family, had been living in exile in the Gulf Emirate of Qatar for years.

He was killed on Wednesday in an Iranian government guest house in Tehran.

Haniyeh had gone to the Iranian capital for the inauguration of the new Iranian President Masoud Pezeshkian.

Iran and Hamas blame Israel for the attack and threaten retaliation.

Israel has not yet commented on the targeted killing of the Hamas leader.

Thousands of people already joined a state-organized mourning ceremony in Tehran on Thursday.

The Hamas leader had been part of the Islamist terrorist organization for decades.

In the ongoing war with Israel in the Gaza Strip, he has been a key figure for international mediators trying to negotiate a ceasefire and the exchange of hostages held in Gaza for prisoners held in Israeli jails.

His death means uncertainty for the future of the negotiations.