The Yemeni military said Thursday that the Houthis, an Iranian-backed militia, had attacked the armed forces of the internationally recognized government in two provinces, an escalation that threatens to reignite Yemen’s long-simmering civil war.

The Houthis targeted “several camps and units of the Armed Forces deployed in Marib and Hadramout provinces,” the Yemeni defense ministry said in a statement posted on social media. The military said its soldiers were killed and injured but did not provide an exact number. Local media outlets reported dozens had been killed.

Hours after the attack, a Houthi military spokesman, Yahya Saree, said the group had launched “a large number of drones and ballistic missiles” at Yemeni military camps in Marib and Hadramout, two oil-rich provinces controlled by the government.

Mr. Saree said the group had launched the attack after they “monitored a large Saudi military mobilization” who were “aiming to escalate” against them.

The Yemeni defense ministry said it would retaliate against the Houthis “at the appropriate time and place.”

Saudi Arabia has led a military coalition in Yemen since 2015 to oust the Houthis and restore the internationally-recognized government, after the militia seized control of the capital Sanaa. The Saudi-led coalition did not publicly comment on Thursday’s attack.

The civil war in Yemen killed hundreds of thousands of people not only from direct violence, but also hunger and disease stemming from the conflict. A fragile cease-fire was agreed between the government and the Houthis in 2022, and Saudi Arabia pulled back from its extensive bombing campaign in Yemen.

The latest round of fighting has prompted fears that the truce is nearing collapse, after months of escalating tensions and intermittent ground skirmishes between government and Houthi forces.

The Houthis have also clashed with Saudi Arabia in recent weeks and declared a blockade of Saudi oil shipping last month in the Red Sea, firing on passing commercial vessels. Mr. Saree warned the Saudi government on Thursday that it “will bear the consequences of any escalation.”

While in the past the Houthis have acted in support of their main ally, Iran, they also have their own reasons for stepping up attacks on Saudi Arabia now, according to researchers who study the group.

Over the past decade, the Houthis have cemented their control of the country’s north, effectively dividing Yemen into two states. Analysts say the group now appears to be looking to consolidate their control over Yemen and its oil resources, believing they have little left to lose after years of political stalemate since the cease-fire.

The province of Marib, where the armed forces were attacked on Thursday, is one of the last strongholds of the Yemeni government in the north.

Located east of the capital Sanaa, it is home to the country’s largest concentration of displaced persons who fled the fighting over the years. Last week, Yemeni authorities declared a state of emergency in Marib to counter a deadly measles outbreak.

Hadramaut, which also came under attack from the Houthis, is home to much of Yemen’s modest oil reserves that have been a key source of funding for the beleaguered government.

Saeed Al-Batati contributed reported from al-Mukalla, Yemen.