Saudi jets launched air strikes on Tuesday against Houthi militiamen close to the kingdom’s southern border with Yemen, after a series of deadly incursions the previous day.

Al Arabiya reported that “tens of Houthi” fighters were killed in the aerial attacks.

The bombing raids came after Houthi fighters managed to cross the border into the Saudi border province of Najran on Monday and kill five Saudi border guards.

A video posted to YouTube claimed to show a Saudi military vehicle being blown up as it hit a Houthi-laid explosive device on a road in the province.

The Houthi attacks led to eight hours of clashes between the tribesmen and Saudi forces on Monday, according to the official SPA news agency.

Yemeni Houthi fighters have regularly crossed the border into Saudi Arabia during Riyadh’s near 15-month long war against the militia, who they claim receive backing from regional rival Iran.

Border clashes have reduced in recent months while UN-brokered peace talks have taken place in Kuwait with the aim of ending the savage conflict in Yemen.

More than 6,800 people have been killed in Yemen since March 2015 when the Saudi-led coalition entered its southern neighbour’s civil war, according to a UN death toll issued in March this year.

More than 80 percent of Yemenis require some form of humanitarian assistance, reports the UN, which has accused all sides of committing atrocities during the conflict.

Riyadh launched its bombing campaign with the aim of pushing back the Houthi fighters who, in an alliance with former Yemeni president Ali Abdullah Saleh, seized control of the capital Sanaa and other parts of the country in September 2014.

The Saudi-led coalition, backed strongly by the United Arab Emirates with ground forces, has sought to re-establish the authority of Yemeni President Abd Rabbu Hadi, who was forced to flee the country when the Houthis advanced on the key port city of Aden.

While the Saudi-led coalition has managed to take back control of southern areas, including Aden, the Houthis remain in control of Sanaa.

Peace talks in Kuwait have failed to produce an agreement to bring an end to the war, and the latest border clashes between Houthi and Saudi forces signal that the conflict looks set to continue for the foreseeable future.