Iran's army chief said on Sunday that Washington lacked the "courage" to initiate a conflict after U.S. President Donald Trump threatened to hit 52 sites in Iran.

"I doubt they have the courage to initiate" a conflict in which the Americans threatened to strike 52 targets, Major General Abdolrahim Mousavi was quoted as saying by state news agency IRNA. 

Trump warned Saturday night that the U.S. would hit Iran harder than ever before if it retaliates over the assassination of Qasem Soleimani, the commander of the Revolutionary Guards' Quds Force foreign operations arm.  

Iran also summoned the Swiss envoy representing U.S. interests in Tehran on Sunday to protest against Trump's words.

A U.S. airstrike on Friday near Baghdad International Airport killed Soleimani and Abu Mahdi al-Muhamdis, the deputy top leader of Iraq's paramilitary Hashd Shaabi forces. 

Iran's army chief dismissed Trump's threats as an attempt to distract the global opinion "from the heinous and unjustifiable act they have done." 

Mohammad Javad Zarif, Iran's top diplomat, also tweeted in response to Trump's post saying any decision to target the country's cultural sites would be a "war crime." 

Iranian Foreign Ministry spokesperson Abbas Mousavi later said on Sunday that Iran is not pursuing war but is prepared and will never forget the actions by the U.S. in Iraq. 

He reiterated the killing was against international law and added that although all parties are advocating restraint, none is offering mediation. 

Iranian Information and Telecommunications Minister Mohammad Javad Azari Jahromi slammed Trump as "a terrorist in a suit" in his tweet.  

"Like ISIS (ISIL), Like Hitler, Like Genghis! They all hate cultures. Trump is a terrorist in a suit. He will learn history very soon that NOBODY can defeat 'the Great Iranian Nation & Culture'," Jahromi said. 

A tide of mourners flooded the Iranian city of Ahvaz Sunday, weeping and beating their chests in homage to the top general.

The funeral processions came a day after a funeral ceremony in Iraq's capital of Baghdad.

"Death to America," mourners chanted as they packed the streets and filled a long bridge spanning a river in the southwestern city, where Soleimani's remains arrived from Iraq before dawn. 

A live broadcast on state television showed crowds in Ahvaz's Mollavi Square with flags in green, white and red depicting the blood of "martyrs." 

"A glorious crowd is at the ceremony," said state television. 

"The presence of children, teenagers, relatives, veterans, families of martyrs of (the Iran-Iraq war) and defenders of Haram (those martyred in Syria) is a glimpse of the glory of this ceremony," it added. 

In Tehran, deputies chanted "Death to America" for a few minutes during a regular session of parliament, the semi-official news agency ISNA reported. 

"Trump, this is the voice of the Iranian nation, listen," speaker Ali Larijani was quoted as saying. 

Soleimani's body will travel next to Mashhad, a holy city in Iran's northeast.

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Rouhani: U.S. made a 'big mistake'

On Saturday, Iranian President Hassan Rouhani visited the house of Soleimani to offer his condolences to the family.

Rouhani said that difficult times would be coming for America as a result of the killing of Soleimani and that the story of Iran as a nation would have been very different without him. 

U.S. made a "big mistake" which will never be forgotten in Iran's history, he added.

Click for live coverage: 

Live: Funeral procession for Iranian military commander killed by U.S.

(Cover: Mourners attend the funeral procession of Qasem Soleimani and Abu Mahdi al-Muhandis in Baghdad, Iraq, January 4, 2020. /Reuters Photo)

(With input from agencies)