Saudi Arabia on Monday accused Lebanon of declaring war against the monarchy following attacks on the Kingdom by the Lebanese Shi‘ite group Hezbollah.

Saudi Gulf affairs minister Thamer al-Sabhan told Al-Arabiya TV that Saad al-Hariri, who announced his resignation as Lebanon’s prime minister on Saturday , had been told that acts of “aggression” by Hezbollah “were considered acts of a declaration of war against Saudi Arabia by Lebanon and by the Lebanese Party of the Devil.”

With tensions rising in the region, the Saudi-led military coalition fighting Houthi rebels in Yemen said Monday it would close all air, land and sea ports to the Arabian Peninsula country to stem the flow of arms to the Houthis from Iran.

The move, which follows the interception of a missile fired toward Riyadh on Saturday, is likely to worsen a humanitarian crisis in Yemen that the UN says has pushed some 7 million people to the brink of famine and left more than half a million infected with cholera.

“The Coalition Forces Command decided to temporarily close all Yemeni air, sea and land ports,” the coalition said in a statement on the Saudi state news agency SPA.

The UN and international aid organizations have repeatedly criticized the coalition for blocking aid access, especially to north Yemen, which is held by the Iran-aligned Houthi rebels battling the Saudi-led coalition.

Saudi Arabia and its Gulf Arab allies have made clear they view Iran as mainly responsible for the Yemen conflict, in which more than 10,000 people have been killed in the past two years.

Saudi Foreign Minister Adel al-Jubeir said Monday on Twitter that Riyadh reserved the right to respond to what he called Iran’s “hostile actions.”

Iranian Foreign Minister Mohammad Javad Zarif responded that Saudi Arabia was blaming Tehran for the consequences of its own “wars of aggression.”

The escalating tensions came during a period of upheaval for the US ally.

On Saturday, 11 Saudi princes, including the country’s most prominent businessman, Alwaleed Bin Talal, were arrested on corruption charges.

Four government ministers and dozens of ex-ministers and government officials were also detained.

The moves were supposedly part of an anti-corruption crackdown but were widely seen as a plot by Crown Prince and heir apparent Mohammed Bin Salman to eliminate rivals and consolidate his power, Slate reported.

The country is facing the transition from King Salman to his son, Mohammed bin Salman.

Since the death of the country’s founder, Abdulaziz, in 1953, all of his successors have been much older men who ruled for relatively short reigns.

The crown prince is only 32, and his elevation over more senior and experienced uncles and cousins has caused resentment, according to the website.

But Saudi law states that the king has to be a male heir of Abdulaziz, who had 45 sons by 22 wives.

The arrests are likely a signal that the young future king is not waiting until he inherits the throne to start exercising power.

In a tweet Monday night, President Trump said he has “great confidence in King Salman and the Crown Prince of Saudi Arabia, they know exactly what they are doing . . . Some of those they are harshly treating have been ‘milking’ their country for years!”