DUBAI (Reuters) - The Saudi-led coalition on Friday launched a military operation north of Yemen’s port city of Hodeidah against what it described as “legitimate military targets”, an incident that could aggravate regional tensions after a weekend attack on Saudi oil installations.

The coalition said it had destroyed four sites used in assembling remote-controlled boats and sea mines to help protect the freedom of maritime navigation.

“These sites are used to carry out attacks and terrorist operations that threaten shipping lines and international trade in the Bab al-Mandab Strait and the southern Red Sea,” coalition spokesman Colonel Turki al-Malki said in a statement.

The Houthi movement in Yemen, which had claimed responsibility for Saturday’s attacks on Saudi oil facilities, said through its Masirah TV that the coalition had breached the U.N. agreement reached in Sweden.

The Western-backed, Sunni Muslim coalition intervened in Yemen in March 2015 against the Yemen Iran-aligned Houthi group after the Houthis ousted the internationally recognized government in Sanaa in late 2014.

The Hodeidah ceasefire and troop redeployment agreement was reached last year at peace talks in Sweden, as a trust-building measure to pave the way for talks to end the war, but stalled for months before the Houthi withdrawal from three Red Sea ports.

Malki added that the Houthis used Hodeidah to “launch ballistic missiles, drones, booby-trapped and remote-controlled boats, as well as for indiscriminate deployment of sea mines.”

The coalition had called on civilians to stay away from the targeted sites and asserted that the military operation was conducted in a way that follows international humanitarian law and that it took the necessary precautionary measures.

“We had forgotten the raids and fear and slept for months in peace. ... But tonight the sounds of explosions and planes frighten us as they continue to fly across the city’s skies,” resident Mohammed Abdullah told Reuters.

On Thursday night, the coalition said it had intercepted and destroyed an explosives-laden boat launched from Yemen by the Houthi group.

The Houthis, who have threatened to widen attacks on Saudi Arabia, have in the past targeted vessels off Yemen, which lies on one side of the Bab al-Mandeb strait at the southern mouth of the Red Sea, one of the world’s most vital oil tanker routes.

The incident comes as the United States and Saudi Arabia consider responses to the assault on Saudi oil facilities, which Washington and Riyadh blame on common foe Iran. Tehran denies any involvement.