CAIRO/Riyadh - Saudi forces and Yemen’s Houthi militia traded heavy artillery fire which blew up part of the main border crossing between the two countries overnight, residents said on Sunday, an escalation of the two-month war.

The Haradh border crossing, the largest for passengers and goods between the world’s top oil exporter, Saudi Arabia, and its impoverished neighbour, was evacuated amid shelling which razed its departure lounge and passport section, witnesses said.

Residents of several Yemeni villages in the area left their homes and fled from the frontier, which has turned into a front line between the kingdom and the Iran-allied rebels. Saudi Arabia has led an Arab coalition bombing the Houthis and backing southern Yemeni fighters opposing the group and loyal to the exiled government in Saudi Arabia headed by President Abd-Rabbu Mansour Hadi.

The Sunni Muslim states believe the Shi’ite Houthis are a proxy for influence by their arch rival Iran, but their campaign has yet to reverse the rebels’ battlefield gains. Residents in the central city of Taiz said Houthi forces and pro-Hadi fighters fired tank and artillery shells at each other throughout the city overnight, and the Houthis seized control of a military base on a strategic mountaintop. Moreover, A boat carrying 460 tonnes of Emirati relief aid docked Sunday in Yemen’s restive port city of Aden, as Saudi-led air raids against Shiite rebels continued across the country.

The shipment, including medical and food supplies, is the second from the United Arab Emirates, which delivered last week 1,200 tonnes of relief aid, said local aid coordinator Ali al-Bikri. Another ship carrying 400 tonnes of diesel also arrived on Friday, said Bikri, who was appointed by Yemen’s government-in-exile.

IN the meanwhile, they are angry and grief-stricken, but Saudi Arabia's minority Shiites refused on Sunday to be provoked by a deadly mosque bombing that authorities called an attempt to promote sectarian strife.

King Salman vowed punishment for anyone linked to the "heinous crime," which killed 21 people.

The interior ministry confirmed the identity of the suicide bomber who blew himself up inside a Shiite mosque in Eastern Province on Friday and said he had links with the Islamic State jihadist group.