The Houthi militia in Yemen launched strikes on southern Saudi Arabia on Tuesday, targeting civilian and economic sites and injuring dozens of people, the Saudi foreign ministry said.

The Houthi attacks injured 73 people, including women and children, in four cities near the Red Sea coast, the Saudi foreign ministry said in a statement, adding that the kingdom would take all necessary measures to defend itself against further strikes.

Saba, a Houthi-run news agency in Yemen, said the militia would issue a statement on Tuesday morning about a “large-scale” military operation in Saudi Arabia.

The Saudi energy ministry said that attacks on energy facilities in the south of the country caused fires at some locations, temporarily disrupting operations. The ministry’s statement did not say who had launched the attacks.

The Iran-backed Houthis are battling for control over Yemen against the internationally recognized, Saudi-supported government of Yemen. The two sides have been fighting since 2014, when the Houthis seized Yemen’s capital, Sanaa. A Saudi-led military coalition intervened to restore the government, plunging Yemen into a yearslong war.

The fighting intensified last week as the Houthis tried to capture territory that could give them more control over shipping routes through the Red Sea, according to local security officials. In July, the militia announced a blockade of Saudi Arabia, and has since launched several attacks on Saudi ships in the region.

The flare-up of the Yemen war this year added a fresh threat to stability in the Middle East, with no visible signs of progress in the efforts to end the war between the United States and Iran.

Volatility has plagued global energy markets since the United States and Israel launched their war on Iran in late February, prompting the effective closure of the Strait of Hormuz to most shipping. The Houthi threat to shipping through the Red Sea, another major shipping chokepoint, has injected more concern about global energy supplies.

This is a developing story.