A Saudi border guard died Tuesday in a landmine blast along the frontier with Yemen, the interior ministry said.
The mine exploded during a patrol in the kingdom's southwestern Jazan district, a ministry statement said.
More than 130 soldiers and civilians have been killed in Saudi Arabia's southern border regions since a Saudi-led coalition began air strikes over Yemen in March 2015.
The coalition supports Yemen's internationally recognised government of President Abedrabbo Mansour Hadi in the fight against Iran-backed Houthi rebels.
The Houthis, allied with former members of the security forces loyal to ex-president Ali Abdullah Saleh, have carried out retaliatory rocket strikes and engaged in firefights along the border.
The coalition has previously said the rebels laid mines along the border.
The insurgents have also launched ballistic missiles further into the kingdom.
In Yemen itself, more than 8,000 people have been killed in fighting since the coalition intervened more than two years ago, the World Health Organization says.