A Saudi-led coalition battling Shiite insurgents appears to be escalating its ground offensive in Yemen, amassing troops in an oil-rich region that is within striking distance of the country’s rebel-held capital.

Hundreds of soldiers from Saudi Arabia, the United Arab Emirates and other Arab countries have been deployed in recent weeks to participate in coalition operations in Marib province, about 75 miles east of Sanaa, the capital, according local fighters and residents.

Thousands of Yemeni militants also are fighting on the side of the coalition against the rebels, known as Houthis, who captured Sanaa and carried out attacks across Yemen over the past year. […]