Five Saudi Arabian border guards were killed on Monday in clashes with "enemy elements" who tried to infiltrate the kingdom's border with war-wracked Yemen, the interior ministry said.

The five were killed in eight hours of fighting when the Saudis confronted "enemy elements of armed groups who tried to infiltrate in several places" in the Najran area, the official SPA news agency quoted a ministry spokesman as saying.

It said the frontier guards backed by the country's army thwarted the attempts to cross the border which began at 0300 GMT.

Southern Saudi Arabia, especially border areas with Yemen, have come under sporadic attack since Riyadh took the lead in March 2015 in an Arab military coalition battling Shiite Huthi rebels who control northern Yemen.

On Monday evening, the coalition said two Saudi officers were killed when their Apache helicopter crashed in Yemen because of bad weather.

They said the aircraft went down in Marib province east of the rebel-held capital Sanaa.

The rebels reported shooting down an Apache between Maarib and the southern Saudi region of Jizan, their media said.

Earlier Monday, a rebel spokesman said the rebels had fired a ballistic missile at a military camp in Jizan, causing casualties and material damage.

Yemeni military sources, meanwhile, reported heavy fighting since Thursday on the Yemeni side of the border between loyalist forces and rebels.

They said five days of fighting in northwestern Yemen have killed 82 people, including 48 rebels.

Around 100 members of the Saudi forces and civilians have been killed in skirmishes, by artillery fire or landmines inside the kingdom's borders since the coalition launched its campaign.

More than 6,400 Yemenis, most of them civilians, have been killed since last March, and the fighting has driven 2.8 million Yemenis from their homes.

Kuwait has hosted Yemen peace talks since April, but the negotiations have failed to make any progress and the Gulf emirate on Thursday gave the warring parties a 15-day ultimatum to strike a deal or leave the country.

Source: AFP