At least 130 Saudi military and civilians have been killed in the conflict, mainly by rockets fired from Yemen
A mine blast killed a Saudi border guard on Sunday on the kingdom's southern frontier with war-wracked Yemen, the interior ministry said.
Three other guards were wounded by the explosion in Jizan province, a ministry spokesman cited by the official SPA news agency said.
Saudi Arabia has led a coalition battling Iran-backed Houthi rebels in its impoverished southern neighbour for the past two years.
At least 130 Saudi members of the security forces and civilians have been killed, mainly by rockets fired from Yemen, since the coalition intervened in support of President Abedrabbo Mansour Hadi in March 2015.
"Saudi Arabia has been attacked with 48 ballistic missiles"
Assiri tongue slip confirm the 2 missiles on Riyadahhttps://t.co/RZ5SlLPWXt
— Hussam Al-Sanabani (@HussamSanabani) April 16, 2017
The Saudi-led coalition also comprises the Gulf monarchies of Bahrain, Kuwait, Qatar and the United Arab Emirates along with Egypt, Jordan, Morocco and Sudan.
In two years, the rebels have fired 47,847 rockets at Saudi territory, as well as "48 ballistic missiles, all of which were intercepted," coalition spokesman General Ahmed Assiri said in an interview broadcast on Sunday by the television channel Al-Arabiya.
"We have an interest in keeping Yemen stable and the borders of the Saudi kingdom secure," Assiri said.
He also said Hadi's government controlled "80 to 85 percent of Yemeni territory" today, two years after the coalition intervened.
However, the Houthis still control the capital Sanaa and much of the northern highlands adjacent to the Saudi border.
The United Nations says that more than 7,700 people have been killed over the past two years in Yemen, which also faces a serious risk of famine this year.