Military spokesman Maj Gen Yahya Rasool said the attack was “a clear assassination by launching an air strike in the midst of a residential area in Baghdad”.
Kataib Hezbollah leaders Wissam Mohammed Sabir Al Saiedi and Arkam Al Alyawi were travelling in a car in the Iraqi capital’s eastern neighbourhood of Al Mashtal when the vehicle was struck by the missiles.
Conflicting reports emerged on the number of those killed, with US officials putting it at one. But militia officials in Iraq told The National that two had been killed, including Al Saiedi, while other news agencies reported three.
The Iraqi government did not give a specific number.
Kataib Hezbollah described Al Saiedi, known as Abu Bakir Al Saiedi, as a “great leader” in its response to the attack. Al Saiedi was a senior commander of the Iran-backed militia, which operates in Iraq and Syria.
He was believed to have managed the group's missile capabilities in Iraq and Syria.
Harakat Al Nujaba, an Iran-backed militia allied with Kataib Hezbollah, promised revenge against the US for the strike, stating: "These crimes will not pass without punishment."
The US had previously promised to retaliate against Kataib Hezbollah and other Iran-backed militias after it blamed the group for an attack on its base in Jordan that killed three US soldiers and injured more than 30.
Pressure on US to withdraw
US forces are engaged in an escalating cycle of violence with Iran-backed militias in Iraq and Syria, which has intensified since the outbreak of the Israel-Gaza war in October.
US strikes against militia targets on Iraqi territory have pushed the Iraqi government to respond to longstanding calls for US forces to leave the country. About 2,500 US troops are stationed in Iraq as part of the international coalition against ISIS.
Maj Gen Rasool said the latest strike showed that US troops were no longer fulfilling their mission in Iraq.
"By this act, the American forces jeopardise civil peace, violate Iraqi sovereignty, and disregard the safety and lives of our citizens. Even more concerning is that the coalition consistently deviates from the reasons and objectives for its presence on our territory," he said.
Iraqi Prime Minister Mohammed Shia Al Sudani, who is supported by Iran-backed militias and parties, initiated the process for US troops to leave last month.
On January 27, Iraq and the US held the first round of talks to end the international coalition's mission, with Baghdad expecting discussions to lead to a timetable for reducing the coalition's presence and to reach bilateral security agreements with state members.
The talks between Baghdad and Washington were then paused after the deadly drone attack the following day on a US base in Jordan, which the US blamed on Kataib Hezbollah.
This latest attack appears to have galvanised pressure from anti-US factions to resume the process. Maj Gen Rasool said the latest attack meant the Iraqi government "more than ever" had to work to end the coalition's presence in the country.
"This trajectory compels the Iraqi government more than ever to terminate the mission of this coalition, which has become a factor for instability and threatens to entangle Iraq in the cycle of conflict, and our armed forces cannot neglect their constitutional duties and responsibilities, which demand safeguarding the security of Iraqis and the land of Iraq from all threats," he said.
Shiite political factions also condemned the attack and linked it to the need for US troops to depart.
Iraq's parliament said it would hold a session on Saturday to discuss "the aggressions on the Iraqi sovereignty", after a request by Shiite legislator Youssif Al Kilabi.
The Co-ordination Framework, the biggest parliamentary group of Iran-backed militias and political parties, said the US had “crossed red lines”.
“The continuation of such attacks will open the door for retaliatory attacks, and it will not stop there,” it warned in a statement.
The leader of the influential militia Asaib Ahl Al Haq, Qais Al Khazaali, called for a request to be sent to the UN Security Council demanding the immediate withdrawal of foreign troops. The US “will not stop this disregard and recklessness”, he said.
Moderate Shiite cleric Ammar Al Hakim, who heads the Al Hikma movement, said that the strike will have consequences for security in the region, adding to its "complexity".
An Iraqi citizen who spoke to The National from the site of the strikes complained of the "unacceptable" attacks.
"I condemn this heinous act that targeted Hashd Al Shaabi forces and their leaders," said Watban Al Khazraji, using the Iraqi name for the Popular Mobilisation Forces, the umbrella organisation for Iran-backed Shiite militias in the country.
"This happens to us two or three times a week. This is unacceptable internationally and customarily," he said.
While praising Al Saiedi as a "great leader", Kataib Hezbollah stopped short of announcing a resumption of attacks against US troops in Iraq and Syria.
The group this month announced it was suspending military operations against US troops in the region.
The decision came days after the three US troops were killed by the drone strike in north-east Jordan, an attack the Pentagon said had the "footprints" of Kataib Hezbollah.
Kataib Hezbollah is part of the Islamic Resistance in Iraq, a loose coalition of Tehran-backed Iraqi militias that includes Harakat Al Nujaba and Kataib Sayyid Al Shuhada.
In contrast to Kataib Hezbollah, these other Tehran-backed groups have vowed to continue attacks against the US.
In a tribute to Al Saiedi broadcast on Telegram, Harakat Al Nujaba called on its fighters to seek “revenge for the martyrs by retributing from America and its aides, partners and interests”.
“Let this be our path and let it be our first cause from now on,” the group said in a statement. “These crimes will not pass without punishment."
The tribute also alluded to Al Saiedi's role in attacking US troops in Iraq and Syria.
“Your fingerprints will remain imprinted on the coffins of the Americans and their extremist organisations in the Levant and Iraq,” it said.
The commander of Kataib Sayyid Al Shuhada militia, Abu Ala Al Walai, also vowed to retaliate in a brief statement on X.
In recent weeks, US drones have been seen hovering over Baghdad, indicating that American troops are tracking down and monitoring the movements of militia operatives.
This latest strike appears to be a more targeted assassination of a militia commander, conducted via drone strike.
Despite the vehicle being hit in the residential and commercial neighbourhood of Al Mashtal, no civilian casualties were reported, suggesting a precise missile was used.
Photos showing debris from the missile suggest it was an R9X, known as the “flying ginsu” and used previously in attacks on several high-profile militants, including Al Qaeda leader Ayman Al Zawahiri, said Charles Lister, senior fellow at the Middle East Institute, in a post on X.
He said the weapon has blades that "slice into the target", while avoiding the use of explosives to prevent collateral damage.
US forces carried out a similar attack on a senior militia leader in Baghdad on January 5. The targeted strike killed Mushtaq Jawad Kazim Al Jawari, also known as Abu Taqwa, a PMF field commander linked to Harakat Al Nujaba.
In January 2020, the Trump administration carried out a targeted assassination of IRGC commander Qassem Suleimani, alongside PMF leader Abu Madhi Al Muhandis, with a drone strike at Baghdad airport.
That strike led to Iran retaliating with a missile attack on a US base in Iraq and a period of heightened tensions across the region.
Aymen Al Ameri contributed to this report.