As general’s body is returned to Iran, president says targets represent the 52 US hostages taken by Iran in 1979

Donald Trump has threatened to hit 52 Iranian sites “very hard” if Iran attacks Americans or US assets in retaliation for the drone strike that killed the Iranian military commander Qassem Suleimani and an Iraqi militia leader.

The US president made the threat in a tweet hours before Suleimani’s body arrived in Iran for burial and ramifications of the killings were reverberating across a nervous region, where many believe the aftermath could spark a new era of bloodletting and instability.

Iranian state television footage showed a tide of mourners packing the streets of the south-west city of Ahvaz early on Sunday to pay their respects and chanting “death to America”. Huge crowds had joined funeral processions in Baghdad and Tehran on Saturday as calls to avenge the Iranian general’s death mounted and the US case for ordering his assassination was increasingly called into question.

Trump tweeted that Iran “is talking very boldly about targeting certain USA assets” in response to Suleimani’s death. He said the US had “targeted 52 Iranian sites” and that some were “at a very high level & important to Iran & the Iranian culture, and those targets, and Iran itself, WILL BE HIT VERY FAST AND VERY HARD”.

“The USA wants no more threats!” Trump said, adding that the 52 targets represented the 52 Americans who were held hostage in Iran for 444 days after being seized at the US embassy in Tehran in November 1979.

Trump did not identify the sites. The Pentagon referred questions about the matter to the White House, which did not immediately respond to a request for comment.

Iran’s foreign minister, Mohammad Javad Zarif, said Trump’s threats breached international law. “Having committed grave breaches of int’l law in Friday’s cowardly assassinations, realdonaldtrump threatens to commit again new breaches,” he tweeted. “Targeting cultural sites is a war crime; – Whether kicking or screaming, end of US malign presence in West Asia has begun.”

Iraq’s parliament is set to meet for an extraordinary session on Sunday where MPs have said they would push for a vote on a resolution requiring the government to request the withdrawal of US troops from Iraq. “There is no need for the presence of American forces after defeating Daesh (Isis),” Ammar al-Shibli, a member of the parliamentary legal committee, told Reuters. “We have our own armed forces which are capable of protecting the country.”

Many Iraqis, including opponents of Suleimani, have expressed anger at the US for killing the two men on Iraqi soil and possibly dragging their country into another conflict.

Play Video 0:35 Qassem Suleimani: moment Iranian general killed by US strike reportedly caught on CCTV – video

The US justification behind Suleimani’s killing centred on there being an “imminent attack” that he had directed, but this has been challenged in some quarters.

The New York Times correspondent Rukmini Callimachi tweeted that two sources privy to the information, held by US intelligence officials, described the case as “razor thin”. Her tweets also detail a scramble to discover Suleimani’s whereabouts once the decision to kill him was made.

The White House transmitted on Saturday evening its formal notification to Congress of Friday’s drone strike that killed Suleimani in Iraq. Many Democrats have criticised Trump for failing to seek advance approval or to notify Congress of the attack.

The classified notification was sent under a US law requiring the administration to notify Congress within 48 hours of committing armed forces to military action or imminent actions.

Nancy Pelosi, the speaker of the House, said in a statement that the White House notification about the attack “prompts serious and urgent questions about the timing, manner and justification of the administration’s decision to engage in hostilities against Iran”.

It was expected that Suleimani’s body will be taken to Tehran and finally to his home town, Kerman, on Tuesday.

Elsewhere in the Middle East, reactions were in sharp contrast. In northern Syria, where Suleimani proved pivotal in saving Bashar al-Assad from defeat, there were celebrations. Sweets were handed out in some towns.

“This general was the devil himself,” said Sobhih Mustafa, in the town of Maarat al-Numan. “His legacy will be written in blood.”

Meanwhile, Iran claimed that the US had sent a note to Tehran through the Swiss embassy, which acts as an intermediary between the two foes, calling for a “proportional response” to the killing of Suleimani. “The Swiss, who represent US interests [in Iran], brought a very unwise message from the Americans, which received a firm response,” Zarif, said on TV. “The Americans made a wrong move and are now worried about its consequences.”

The deputy commander of the Islamic Revolutionary Guard Corps, Brig Gen Ali Fadavi, said the US “resorted to such means as diplomacy this morning [Friday] and even told us ‘if you want to take revenge, do it in a way that’s proportional to what we did’”.

“But they cannot decide anything [for us],” Fadavi added, according to the Iranian English-language news site Iran Front Page. “That will take place at the most opportune time and in the best manner possible.

“Soon we will see that the Americans will not be there in the region,” he said.