The US secretary of state, Mike Pompeo, has hit out at Iran after briefing Donald Trump about US strikes against a militia group in Iraq and Syria in which 25 fighters were reportedly killed.

The Pentagon said the attacks were “defensive strikes” against the Kata’ib Hezbollah militia group, which US officials said was backed by Iran, two days after a US civilian contractor was killed in a rocket attack on an Iraqi military base.

“We will not stand for the Islamic Republic of Iran to take actions that put American men and women in jeopardy,” Pompeo told reporters after the briefing, which took place at Trump’s Mar-a-Lago club in Florida.

Mark Esper, the defence secretary who also attended the briefing, said the strikes had been successful and that officials discussed other options with Trump.

Iraqi security and militia sources said at least 25 militia fighters had been killed and at least 55 wounded following three US airstrikes in Iraq on Sunday. At least four local commanders from the Iranian-backed Shia Muslim group were among the dead, the sources said, adding that one of the strikes had targeted the militia group’s headquarters near the western al-Qa’im district on the border with Syria.

The Pentagon said it also targeted two locations used by Kata’ib Hezbollah in Syria.

The five sites across the two countries included weapons storage facilities and command and control locations Kata’ib Hezbollah had used to plan and execute attacks on coalition forces, it said.

A US official, speaking on the condition of anonymity, said the strikes were carried out by F-15 fighter jets.

The US had accused the group of the 30-plus rocket attack on Friday that killed the civilian contractor and injured four US service members as well as two members of the Iraqi security forces near the oil-rich city of Kirkuk.

“In response to repeated Kata’ib Hezbollah attacks on Iraqi bases that host Operation Inherent Resolve (OIR) coalition forces, US forces have conducted precision defensive strikes ... that will degrade KH’s ability to conduct future attacks against OIR coalition forces,” chief Pentagon spokesman Jonathan Hoffman said.

Earlier this month, Pompeo, blamed Iranian-backed forces for a series of attacks on bases in Iraq and warned that any attacks by Tehran or proxies that harmed the US or allies would be answered with a decisive response.

Tensions have heightened between Tehran and Washington since last year when Trump pulled the United States out of Tehran’s 2015 nuclear deal with six powers and reimposed sanctions that have crippled Iran’s economy.