Saudi Arabia announced on Friday the deaths of three Saudis, including a pilot, in Thursday's strikes on Riyadh airport, which were claimed by the Houthis of Yemen.

Hostilities between these pro-Iranian fighters and Saudi Arabia, which supports the Yemeni government, intensified in September after the Houthis seized the Red Sea coastline following a lightning offensive.

In a statement, the civil aviation authority indicated that the airport had been the target of "two attacks: the first targeted airport facilities, while the second targeted an aircraft belonging to the Saudia company."

She added that "three Saudi citizens" had died in the attacks and that several people of different nationalities had been injured.

Saudia Airlines, the national carrier, announced that one of its pilots was killed and one of its planes damaged on Thursday, referring to it as an "incident".

In total, six people were killed in the space of a few days in Houthi-claimed attacks against Saudi airports.

- "Military blackmail" -

Faced with the scale and frequency of Houthi attacks on the Saudi capital, unprecedented since the resumption of hostilities in July, Riyadh will not give in to the "military blackmail" of the pro-Iranian fighters, a regional source familiar with Saudi government policy told AFP.

Saudi Arabia "rules out a truce or ceasefire" until the Yemeni government forces it supports have recovered the territories recently seized by the Houthis, the source warned on condition of anonymity.

On Thursday alone, the Houthis claimed responsibility for three attacks on Riyadh airport.

Hostilities between pro-Iranian fighters, who have controlled the Yemeni capital Sanaa and large parts of the country for more than a decade, and the government reignited in July after years of relative calm.

Since then, pro-Iranian fighters have regularly bombed oil facilities in the Saudi kingdom, the world's leading crude oil exporter, and on Thursday called on staff at these sites to leave.

They also again urged airlines to avoid Saudi airspace.

Riyadh airport asked passengers to check with their airline that their flight was not cancelled before traveling there, and Washington called on its citizens to be "more vigilant" after the attacks.

Loud explosions were heard Thursday as far away as the heart of the capital, prompting diplomats to seek refuge in the embassy district, and businesses to evacuate their staff in the business district.

International schools have also taken precautions, according to residents' accounts, with children in some cases taking refuge in the basement as a safety measure.

- New humanitarian crisis -

Alongside the strikes in Saudi Arabia, fighting continues in Yemen, with more than 400 deaths since the launch on Monday of Operation "Yemen Dawn" by government forces, with the support of Riyadh's fighter jets.

The objective is to push back the Houthis who, at the end of their offensive in September, have strengthened their hold on the strategic Bab el-Mandeb strait, linking Asia to Europe via the Suez Canal.

The government claimed "victories on several fronts," a claim denied by the Houthis. Military sources on both sides reported no major developments on the front lines.

The resumption of hostilities has displaced more than 200,000 people in Yemen, according to the International Organization for Migration (IOM), which on Wednesday expressed alarm at the lack of funding needed to deal with this new humanitarian crisis in the poorest country on the Arabian Peninsula.

Riyadh and its allies have repeatedly called for international support in recent weeks, particularly from the United States, without success so far.