Police in Saudi Arabia said Wednesday they had arrested two suspected militants and were hunting two others who fled following shootouts and raids that netted automatic weapons and a bomb belt.

The gunfire occurred in separate districts of Riyadh on Tuesday night as officers pursued an investigation into "deviant groups," the interior ministry said in a statement.

A Saudi Border Guard died Monday in an exchange of fire on the border with Yemen, the interior ministry said on day two of a major anti-rebel offensive inside Yemen.

A post in Jazan's Harth district came under fire from Yemen early Monday, sparking the firefight in which the soldier was killed, a ministry statement said.

Saudi-backed loyalist forces in Yemen pressed an offensive against Shiite Huthi rebels on Monday, the second day of a major campaign aimed at retaking the capital a year after its fall.

Fighters loyal to exiled President Abedrabbo Mansour Hadi launched their much anticipated attack against the Iranian-backed rebels and their allies in the key province of Marib.

Five Saudi soldiers have died on the border with Yemen, the Saudi-led coalition said late on Sunday as forces inside Yemen began a major offensive against rebels.

A coalition statement did not say how the army soldier and four Border Guard troops died in the kingdom's southern Najran region.

Saudi Arabia's military blamed a "technical error" for a helicopter crash that killed a pilot during a training mission on Sunday.

The air force machine went down in the Taif area, more than 800 kilometers (500 miles) from the border with Yemen.

Two days after a crane collapse killed 107 people at Mecca's Grand Mosque in Saudi Arabia, the region's governor on Sunday filed an investigative report, official media said.

Prince Khaled al-Faisal "has submitted today the results of the investigation," the Saudi Press Agency said.

The deadly collapse of a construction crane in Saudi Arabia's holy city of Mecca has highlighted the controversial pace of high-end urban development in the birthplace of Islam.

More than 100 people died on Friday when the crane toppled into a courtyard of the Grand Mosque, one of Islam's holiest sites, during a thunderstorm.

Saudi Arabia's King Salman vowed on Saturday to find out what caused a crane collapse that killed 107 people at Mecca's Grand Mosque ahead of the annual hajj pilgrimage.

The hajj, a pillar of the Muslim religion which last year drew about two million faithful, will take place despite Friday's tragedy, Saudi authorities said as crowds returned to pray a day after the incident.

Saudi authorities said Saturday the annual hajj pilgrimage would go ahead despite a crane collapse that killed 107 people at Mecca's Grand Mosque, where crowds returned to pray a day after the disaster.

Hundreds of thousands of pilgrims have already arrived in Mecca for the hajj, one of the world's largest religious gatherings which last year drew two million worshippers.

Hundreds of rebels protested Friday in Sanaa over claims that Saudi Arabia, home to Islam's holiest sites and host to the hajj, was denying Yemenis the right to attend this year's pilgrimage.

Dressed in the white shrouds worn by pilgrims and brandishing assault rifles, they shouted "No to politicizing the hajj."