Egyptian President Abdel-Fattah El-Sisi told King Salman of Saudi Arabia that the security of the Gulf is a “red line” and an “integral part of Egyptian national security” in a phone call after Egypt joined a Saudi-led regional military operation to halt the advance of Shia Houthi rebels in Yemen.

Egypt is heeding the calls of the Yemeni people to restore stability and legitimacy in Yemen and maintain Arab identity, a statement from the Egyptian presidency read.

On Thursday, Saudi Arabia and regional allies carried out airstrikes against Houthi rebel sites in the Yemeni capital Sanaa, after Houthi fighters on Wednesday stormed the southern coastal city of Aden. Yemeni President Abd-Rabbu Mansour Hadi has fled to Riyadh.

Egypt announced on Thursday that it will deploy navy and air forces to participate in the operation.

El-Sisi told the Saudi king that the challenges facing the Arab region and threatening its people are one and the same and should be faced with a united front.

The Saudi king, according to the statement, thanked Egypt for its “political and military support” for the military operation in Yemen.

El-Sisi also received a call from Prince Mohammed Bin Salman, the Saudi defence minister, who updated the president on the latest news regarding the military operation in Yemen.

Sudan and Jordan have confirmed that they have joined Qatar, Kuwait, Bahrain and the United Arab Emirates in the Saudi-led military coalition, while Saudi Arabia has said that Pakistan and Morocco will also join.

The operation comes ahead of the Arab League Summit on Saturday in Egypt’s Sharm El-Sheikh, where regional security issues are expected to be at the top of the Arab leaders’ agenda.