One day after the US killed a top Iranian general — a major escalation between the two countries — another strike was reportedly conducted in Iraq, this time targeting members of Iranian-backed paramilitaries in the country.

Early Saturday morning local time, a two-car convoy containing members of the Popular Mobilization Forces, the overarching group for those Iranian-backed militias, was struck, killing at least five people, according to multiple international media outlets.

Though the target hasn’t been made public, a PMF spokesperson confirmed the attack to the AP.

The US has yet to say whether it conducted the attack. But it comes one day after President Donald Trump’s administration, operating in dubious legal territory, killed Maj. Gen. Qassem Soleimani, the head of Iran’s elite Quds force and arguably the second most powerful military official in the country.

Tensions between Tehran and the Washington had already been high in the preceding week, as I and Vox’s Libby Nelson noted:

The attack comes after days of escalating tensions. An American contractor was killed near Kirkuk, Iraq, last week, and four military members were injured in an attack by Iranian-backed militia Kataib Hezbollah. A retaliatory strike by the US killed 25 members of the militia and injured more than 50. Then, on New Year’s Eve on Tuesday, militia members attacked the US Embassy in Baghdad.

According to a Pentagon statement Thursday night, the US killed Soleimani to deter “future Iranian attack plans” (though neither the Pentagon, Secretary of State Mike Pompeo, his department, or the president provided details about those planned attacks). It’s not clear — if the US confirms its role in Saturday’s attack — whether the reason will be the same for this latest strike in Iraq.

Iran has yet to respond to this latest strike, but promised “forceful revenge” for the earlier one.

This is a developing story, and a number of details about the attack are still unknown. Here’s what we know and don’t know as the story unfolds.

What we know

Several people were killed when a two-car convoy containing members of the Popular Mobilization Forces, the overarching group for Iranian-backed militias in Iraq, was struck early Saturday morning local time, multiple international media outlets reported.

The PMF confirmed the attack, saying one of its medical convoys had been targeted while traveling in Taji in the north of Baghdad, the AP reports.

Iraqi officials told the AP five people were killed; Reuters reported one additional person was killed, and three people were injured.

Saturday, Iraq’s Joint Operations Command rebutted reports of an airstrike, saying in a statement: “The Joint Operations Command calls for caution in reporting and spreading rumors especially at this time.”

A spokesperson for the US and its allies in the fight against ISIS tweeted a similar denial Saturday, writing that the US and its partners “did NOT conduct airstrikes near Camp Taji (north of Baghdad) in recent days.”

What we don’t know