Iran declared Thursday a day of mourning following twin blasts that killed at least 103 people near the grave of slain general Qasem Soleimani in the country's south.

According to the media, two bombs in quick succession struck a crowd commemorating slain general Qasem Soleimani on the anniversary of his killing on Wednesday.

"Following the terrorist incident in Kerman, the government declared tomorrow (Thursday) a day for public mourning across the country," state television announced on Wednesday.

The explosions, dubbed a "terrorist attack" by state media, occurred a day after Iran-ally and leader of Hamas, Saleh al-Aruri, was murdered in a drone attack on a southern neighborhood of Beirut, which Lebanese officials blamed on Israel. Tensions were high in the Middle East.

As supporters gathered to commemorate the fourth anniversary of Soleimani's death in a US drone strike just outside Baghdad airport, explosions remained close to the Saheb al-Zaman Mosque in Kerman, his hometown in the south where he is buried.

Rahman Jalali, the deputy governor of Kerman, described the blasts as a "terrorist attack".

The incident was not immediately attributed to anyone.