Riyadh: Two Saudi soldiers have been killed in a clash with unidentified gunmen who fired on them from across the border with Yemen, the interior ministry said on Thursday.

A border guard patrol in the southwestern province of Asir “came under heavy gunfire on Wednesday morning from unknown sources inside Yemeni territory,” said the ministry.

Ministry spokesman Mansour Al Turki said that a border guard patrol in Asir responded to the attack.

The attack triggered a gun battle that resulted in the death of sergeant Abdul Razaq Al Qhamidi and soldier Mohammad Al Qah’tani, it said in a statement.

The Saudi authorities were coordinating with their counterparts in Yemen to investigate the attack.

Asir borders Yemen’s northern Saada province, which is largely controlled by a Al Houthi rebels.

On Sunday, Saudi authorities announced that they had arrested 3,742 smugglers and illegal immigrants on the Yemeni border during February and March.

The kingdom’s long and porous border with Yemen is frequently crossed by smugglers as well as Islamists seeking to join Al Qaida militants in the impoverished Arabian Peninsula nation.