SANAA, Sept. 9 (Xinhua) -- Yemen's Houthi group said Wednesday that dozens of "Saudi airstrikes" had struck areas under its control over the past 12 hours, as cross-border attacks and expanding ground battles pushed the country's conflict into a new phase of escalation.

Houthi military spokesman Yahya Sarea said in a statement on social media platform X that "Saudi enemy warplanes" had carried out 55 airstrikes over the past 12 hours, hitting Al-Jawf and Saada in northern Yemen, northeastern Marib and Al-Bayda in the center, and the western provinces of Taiz and Hodeidah.

He warned that the strikes "will not go unanswered," but gave no details on the targets, casualties or damage.

There was no immediate comment from Saudi Arabia on Sarea's latest claims.

The reported strikes came a day after the Houthis launched a wave of missile and drone attacks against targets in southern Saudi Arabia, including energy facilities and a military air base. Saudi authorities said 73 people were injured and fires broke out at several facilities.

The cross-border exchanges have unfolded alongside a sharp escalation inside Yemen, where government forces and the Houthis are fighting on several fronts, most intensely in the country's western areas.

Fierce clashes have centered on areas near the Bab al-Mandab Strait, the narrow waterway connecting the Red Sea with the Gulf of Aden and a critical route for international shipping. Government forces have been seeking to halt Houthi advances toward positions overlooking the strategic strait, according to local military sources.

Yemeni government forces said in a statement carried by state-run Saba TV on Wednesday that several Houthi commanders involved in operations near the Bab al-Mandab Strait had been killed or captured. The statement provided no further details, and the Houthis did not immediately comment on the claim.

In the same statement, the forces said their naval units exchanged fire with Houthi boats in the Red Sea, forcing them to retreat toward the Houthi-held port city of Hodeidah.

Farther north, the government forces said on Wednesday they had made additional advances in Al-Jawf and cut Houthi supply routes as part of an expanding offensive in the northern province, which borders Saudi Arabia and lies east of the Houthi-held capital Sanaa.

The widening hostilities are taking a growing humanitarian toll, triggering a new wave of displacement across western and southern Yemen.

The government-run Executive Unit for the Management of Displaced Persons Camps said Wednesday that 1,367 families had been displaced from areas in the southwestern province of Taiz, the Red Sea province of Hodeidah and the southern province of Lahj over the previous 24 hours.

That brought the number of families recorded as displaced across the three provinces since the beginning of September to 6,145, according to the unit.

The latest escalation threatens to unravel several years of relative calm on Yemen's major frontlines following a UN-brokered truce that took effect in April 2022. Although the truce formally expired six months later, large-scale fighting remained largely contained until the recent flare-up.

Yemen has been mired in conflict since late 2014, when the Houthis seized Sanaa and much of northern Yemen, forcing the internationally recognized government out of the capital.

A Saudi-led coalition intervened in the conflict in 2015 in support of the Yemeni government. Years of fighting have left the country deeply divided and created a protracted humanitarian crisis.