RIYADH, Saudi Arabia — In a potentially major escalation of the months-long war, Yemeni rebels fired a Scud missile into Saudi Arabia early Saturday. The attack suggests that despite more than two months of airstrikes by a Saudi-led coalition, Yemen's Shiite rebels, known as Houthis, still have the military firepower to threaten cities inside Saudi Arabia.

According to the official Saudi Press Agency, two missiles launched from a Patriot missile battery shot down the Scud before dawn near the southwestern city of Khamis Mushait. The agency did not report any casualties in the attack, the first use of a Cold War-era Scud by the rebels since Saudi-led airstrikes targeting the Houthis began in late March.

Yemen's state news agency SABA, now controlled by the Houthis, said the rebels fired the Scud. The Houthis are allied with military and security forces loyal to former Yemeni President Ali Abdullah Saleh.

Khamis Mushait is home to the King Khalid Air Base, the largest such facility in that part of the country. Saudis on social media reported hearing air raid sirens go off around the city during the attack.

The Yemeni military was widely believed to possess around 300 Scud missiles, most of which fell into the hands of the rebels. In April, the spokesman for the Saudi-led coalition, Saudi Brig. Gen. Ahmed Asiri, implied that the Scud arsenal in Yemen had been seriously degraded as a result of the airstrikes.

"As coalition forces, we confirm that all Houthi capabilities were targeted, foremost their ballistic missiles," Asiri said at the time.

On Saturday, Asiri told the Saudi-owned Al-Hadath news channel that coalition forces have destroyed "most of" Yemen's Scuds.

Abdulkhaleq Abdullah, a professor of political science at United Arab Emirates University, said Saturday's attack was a way for the Houthis and their allies to signal that they still have fight left despite months of airstrikes. The Emirates is a member of the Saudi-led coalition.

"It is an escalation," Abdullah said. "It is clear now there has not been a knockout and a complete demolition of Houthi firepower."

The Saudis and Western powers accuse the Houthis of receiving military support from Shiite power Iran as part of a larger proxy war between the Sunni kingdom and the Islamic Republic across the Mideast. Tehran and the rebels deny the allegations, though Iran has acknowledged sending humanitarian aid to the Houthis.

Saudi Arabia leads a coalition targeting the rebels in airstrikes in support of Yemen's exiled President Abed Rabbo Mansour Hadi. Those strikes have targeted arms caches and Scud missile sites around the country.

The coalition responded to Saturday's attack by targeting and damaging the Scud launcher, which was located south of the Houthi stronghold city of Saada, according to SPA.

Yemeni security officials said coalition planes launched at least six airstrikes early Saturday against a Houthi convoy heading toward Saada. Airstrikes also hit a convoy in Amran province, which Houthi and tribal officials said was transporting livestock. The officials spoke on condition of anonymity because they were not authorized to talk to the media.

Saudi Arabia is the world's largest oil exporter. Its major oil fields are located in the east of the country, far from Khamis Mushait.

The United States has provided logistical support to the mostly Arab coalition. U.S. military officials in the region had no immediate comment.

The Houthis began their advance in September, sweeping down from the north and capturing the capital, Sanaa. They held top officials, including Hadi, under house arrest until Hadi fled, first to the southern port city of Aden, then to Saudi Arabia as the rebels closed in.

The Saudi-led air campaign and ground fighting have killed more than 1,000 civilians and displaced more than 1 million people since mid-March, the spokesman for the U.N. secretary-general, Stephane Dujarric, told reporters Wednesday.

The offensive, now in its third month, has so far failed to force the Houthis to withdraw from any territory they hold or blunt their advance in southern Yemen.

Security officials said fierce fighting on the ground continued Saturday in the areas of Abyan, Haja, and Taiz, as coalition planes hit targets in Abyan, Amran and Saada.

On Friday, the Houthis and Saleh's forces launched a ground offensive targeting the Saudi border, prompting the kingdom to fire artillery and launch Apache attack helicopters, SPA also reported. It said "scores" of rebel forces were killed, along with four Saudi soldiers, in a battle that lasted from dawn till noon.

Planned Yemeni peace talks were postponed last month just two days before they were to have begun on May 28 and no new date has been officially announced.

After several days of negotiations in neighboring Oman, Houthi officials say their delegation is heading to Moscow at the invitation of the Russian Foreign Ministry. Russian officials did not immediately comment on the reported visit.

The strikes, as well as a Saudi-led air and sea blockade, have caused food, water and medicine shortages, sparking a humanitarian crisis in the Arab world's poorest country.

The Soviet Union developed Scuds during the Cold War and exported the ballistic missiles to several countries, including Yemen.

Scud strikes in Saudi Arabia have been fatal in the past. On Feb. 25, 1991, an Iraqi-fired Scud evaded a Patriot strike and hit a U.S. base in Dhahran, Saudi Arabia, killing 28 American soldiers.

Associated Press writers Adam Schreck in Dubai, United Arab Emirates, Ahmed al-Haj in Sanaa, Yemen, and Jon Gambrell and Maamoun Youssef in Cairo contributed to this report.