Iran’s allies and proxy forces across the Middle East promised to take revenge against the US for its killing of top Iranian general Qassem Soleimani on Friday, setting the scene for retaliatory attacks throughout the region and beyond.

Hassan Nasrallah, leader of the powerful Lebanese Shia group Hezbollah and a key partner in Iran’s regional network, vowed to continue Soleimani’s “tireless struggle” in a statement mourning his death.

“It will be the responsibility, duty, and action of all the resistance fighters and mujahideen throughout the world to take revenge from his criminal killers who are the worst villains of this world,” Nasrallah said in the statement.

“It will not be permitted for this pure blood which was unjustly shed to go to waste,” he added.

For more than two decades, Soleimani was the architect of Iran’s expanding influence across the Middle East. He travelled the region in his dual roles of diplomat and military commander to build and support a “resistance bloc” – an alliance of Shia militant groups that would facilitate Iran’s regional ambitions and counter US influence.

Tensions high as Trump approves new Iran sanctions: In pictures Show all 17 1 /17 Tensions high as Trump approves new Iran sanctions: In pictures Tensions high as Trump approves new Iran sanctions: In pictures Iran claims that in this picture released by Iran state TV, their surface-to-air missile is seen as it shoots down a US surveillance drone EPA Tensions high as Trump approves new Iran sanctions: In pictures This photo shows US RQ-4A Global Hawk unmanned surveillance drone. A drone of this model was shot down by Iran on Thursday 21 June AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures An oil tanker is on fire after it was subject to a suspected attacked at the Gulf of Oman on June 13. The US has blamed Iran for the attack Reuters Tensions high as Trump approves new Iran sanctions: In pictures Iran claims that in this picture released by Iran state TV, debris from the downed US drone is seen after it was recovered from Iranian waters AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures Smoke billows from an oil tanker after it was subject to a suspected attacked at the Gulf of Oman on June 13 Reuters Tensions high as Trump approves new Iran sanctions: In pictures US President Trump holds up a signed executive order to increase sanctions on Iran on 24 June AP Tensions high as Trump approves new Iran sanctions: In pictures Iranian President Rouhani stated in a televised address that the White House is "afflicted by mental retardation" following the increase in sanctions on 25 June EPA Tensions high as Trump approves new Iran sanctions: In pictures An Iranian navy boat tackles the fire on the Norwegian owned Front Altair oil tanker after it was hit in a suspected attack AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures Iran claims that in this picture released by Iran state TV, debris from the downed US drone is seen after it was recovered from Iranian waters AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures Smoke billows from an oil tanker after it was subject to a suspected attacked at the Gulf of Oman on June 13 Reuters Tensions high as Trump approves new Iran sanctions: In pictures A screenshot from a video released by the US Department of Defense that the US claims to show Iranian removing an unexploded limpet mine form the hull of the Japan-owned ship that was attacked in the Gulf of Oman on June 13 Getty Tensions high as Trump approves new Iran sanctions: In pictures An item reportedly found on the Japan-owned oil tanker that was attacked on June 13 in the Gulf of Oman AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures A handout photograph from the US Department of Defense shows a composite material that the US claim was left behind on the hull of the Japan-owned oil tanker following the removal of an unexploded limpet mine Getty Tensions high as Trump approves new Iran sanctions: In pictures A view from the cabin of an Iranian navy boat as it tackles the fire on the Norwegian owned Front Altair oil tanker after it was hit in a suspected attack EPA Tensions high as Trump approves new Iran sanctions: In pictures Release by US government A picture released by U.S. Central Command shows damage to the hull of the oil tanker Kokuka Courageous. The picture suggests that the ship is 'likely' to have been hit by a mine as the US Secretary of State Mike Pompeo moves to blame Iran for the suspected attack Reuters Tensions high as Trump approves new Iran sanctions: In pictures Smoke billows from an oil tanker after it was subject to a suspected attacked at the Gulf of Oman on June 13 Reuters Tensions high as Trump approves new Iran sanctions: In pictures Release by US government A picture released by U.S. Central Command shows damage to the hull of the oil tanker Kokuka Courageous. The pictures suggests that the ship is 'likely' to have been hit by a mine as the US Secretary of State Mike Pompeo moves to blame Iran for the suspected attack EPA

Stretching from Tehran to the Mediterranean coast, through Iraq, Syria, Lebanon and Yemen, this network of non-state actors received significant military and financial support, which gave Iran significant influence across the region.

Those proxy forces Soleimani spent years supporting and building are now likely to be the main conduit through which Iran strikes back against US interests.

Iraq, which has been the focus of rising US-Iran tensions in recent weeks, is the most likely location.

There, the leader of the pro-Iran Badr Organisation militia, Hadi al-Ameri, called on “national forces to unify their ranks to expel foreign forces” from Iraq in retaliation for the killing.

Ameri, referring to the simultaneous killing of Abu Mahdi al-Muhandis, founder of the Iraqi Shia militia Kata’ib Hezbollah, condemned the “criminal acts that targeted the two leaders”, according to Iraqi state television.

The Badr Organisation is just one part of a network of Shia militias that Iran financed, equipped and trained to fight America, in the years after the US invasion of Iraq in 2003.

Paramilitary group Asaib Ahl al-Haq, Kata'ib Hezbollah and the Badr Organisation all had close ties to Soleimani, the leader of Iran’s elite Quds Force, and fall under the umbrella of Iraq’s Popular Mobilisation Forces (PMF). Together they number more than 140,000 fighters, and while they fall under the authority of Iraq’s prime minister, the PMF’s top brass are politically aligned with Iran.

But the assassination has also angered forces inside Iraq that do not fall under the sway of Iran.

Influential Shia cleric Muqtada al-Sadr, who has in recent years emerged as an important counter to Iran’s influence in the country, also announced the mobilisation of factions under his command in response to the killing.

He described the strike against Soleimani as “targeting jihad, the opposition and the revolutionary spirit of the state”.

“As I am responsible for the Iraqi national resistance, I give my orders to the Mujahedin, particularly (Al-Mahdi Army) and (The Promised Day Brigade), as well as other (patriotic) and (disciplined) factions under our command to be ready to defend Iraq”, Sadr tweeted to his 784,000 followers.

The leader of Yemen’s Houthi movement, Mohammed Ali al-Houthi – another regional ally of Iran – also condemned what he dubbed an assassination and called for a “swift and direct response”.

In Gaza, Hamas – which has long enjoyed financial and military support from Tehran – condemned Soleimani’s killing and sent its “dearest condolences” to Iran.

Gaza-based Hamas official Basem Naim wrote on Twitter that the assassination “opens the doors of the region to all possibilities, except calm & stability. USA bears the responsibility for that”.

But there were celebrations, too, in places that have felt the brunt of Soleimani’s force. In Syria, where the general masterminded a full-throated military intervention to crush opposition to the rule of Bashar al-Assad, many took to the streets in celebration. In Idlib, the last rebel bastion in the country, people handed out sweets to mark the occasion.

“I haven’t seen Syrians so happy and celebrating like this since Trump ordered a strike on Assad regime in 2018,” said Mazen Hassoun, a Syrian journalist from Raqqa now living in Germany.

In Basra, Iraq, where Iran-backed militias have launched a crackdown against anti-government protesters in recent weeks, videos were shared showing people dancing in the streets.

There was cause for celebration too from Israel, America’s closest ally in the Middle East and Iran’s top regional foe.

Israeli prime minister Benjamin Netanyahu said on Friday that the US had the right to defend itself by killing Soleimani.

“Just as Israel has the right of self-defence, the United States has exactly the same right,” Netanyahu said in a statement issued by his office.

“Qassem Soleimani is responsible for the death of American citizens and many other innocent people. He was planning more such attacks.”

“President Trump deserves all the credit for acting swiftly, forcefully and decisively,” he added.

Outside the Middle East, US allies and foes alike predicted significant upheaval to come.

“We are waking up in a more dangerous world. Military escalation is always dangerous,” France’s deputy minister for foreign affairs, Amelie de Montchalin, said on RTL radio. “When such actions, such operations, take place, we see that escalation is under way.”

Russia’s Foreign Ministry, via an unnamed diplomat quoted by the state-run TASS news agency, condemned the killing as “an adventurist step that would lead to growing tensions throughout the entire region”.

China described itself as “highly concerned”.

“Peace in the Middle East and the Gulf region should be preserved,” Chinese Foreign Ministry spokesperson Geng Shuang said. “We urge all parties concerned, especially the United States, to maintain calm and restraint and avoid further escalation of tensions.”