Tens of thousands of people from across Iraq and Palestine joined Iran on Saturday in honouring the death of Iran's military commander Qassem Soleimani, Iraqi militia leader Abu Mahdi al-Muhandis and others who were killed a day earlier in a US drone strike.

Soleimani, a 62-year-old general, was Iran's most prominent military commander and the architect of its spreading influence in the Middle East. Muhandis was the deputy commander of Iraq's Popular Mobilisation Forces (PMF) umbrella body of paramilitary groups.

Iranians young and old thronged the streets across Iran, waving national flags and breaking into mass chants of "I am Soleimani" as they mourned his killing.

“I don't feel safe anymore. He was a hero. I am not a religious or pro-regime woman,” said Shahnaz Milaninia, 61, a resident of an affluent Tehran district when contacted by Reuters.

“But I respect Soleimani. He sacrificed his life in order to protect us.”

In Iraq, an elaborate funeral procession organised by the PMF was held in Baghdad.

The procession began in Baghdad's heavily fortified Green Zone, moving towards the Shia holy city of Kerbala and ending in the Shia holy city of Najaf where Muhandis and the other Iraqis killed will be buried.

Soleimani's body will be transferred to the southwestern Iranian province of Khuzestan that borders Iraq, then on Sunday to the Shia holy city of Mashhad in the northeast and from there to the capital Tehran and on to his hometown Kerman in the southeast for burial on Tuesday, Iranian state media reported.

Marchers waved Iraqi and militia flags in a sombre atmosphere, with Iraqi Prime Minister Adel Abdul Mahdi and Iraqi militia commander Hadi al-Amiri, a close Iran ally and the top candidate to succeed Muhandis, attending the procession.

Meanwhile, hundreds of Palestinians in the Gaza Strip also mourned the death of the Iranian Revolutionary Guards commander.

Leaders of the Hamas group, which rules Gaza, and of the Palestinian Islamic Jihad faction, both backed by Iran, joined mourners at a tent erected in Soleimani's honour in the heart of Gaza City.

Flags of the United States and Israel were laid on the ground for visitors to tread on as they entered, passing murals of Soleimani. The flags were later set on fire.

“We are loyal to those who stood with the resistance and with Palestine and we hold the US administration and the Zionist occupation fully responsible for the consequences of this deplorable crime,” said Ismail Radwan, a Hamas official.