SANAA, Yemen –  The Saudi-led coalition fighting Shiite rebels in Yemen doubled its near-daily airstrikes Monday in the central province of Marib and the adjacent border area of Jawf, in order to allow allies on the ground to push north toward insurgent strongholds, authorities said. There was no immediate word on casualties.

Marib's pro-government forces also received major reinforcements, including hundreds of Saudi-trained troops, ambulances and armored personnel carriers manned by Saudi and Emirati soldiers, pro-government officials said.

The forces aim to take Saada, the main northern stronghold of the Houthi rebels, they added.

Yemen's conflict pits the Iran-allied Houthis and troops loyal to former President Ali Abdullah Saleh against an array of forces including southern separatists, local and tribal militias, Sunni Islamic militants as well as troops loyal to President Abed Rabbo Mansour Hadi. Pro-government forces recently pushed the Houthis out of several key southern areas.

Meanwhile, in Yemen's third-largest city, Taiz, shelling by Houthi and pro-Saleh forces killed 14 civilians, independent security and medical officials and witnesses said.

In Aden, al-Qaida militants and other Islamic extremists continue to patrol the streets. Hundreds of al-Qaida militants hold some key areas in the port city, exploiting a vacuum left by pro-government forces pushing north, a high-ranking pro-Hadi security official and two other high-ranking pro-Hadi police officers, all in Aden, said.

"We have a shortage of men," the state security official said. "Getting equipment (from coalition countries) is easy. Getting men to operate them is hard."

He said Hadi's government, in response, sent youths to receive police training in Saudi Arabia and the United Arab Emirates.

All officials requested anonymity because they are not authorized to brief reporters, while witnesses feared reprisals.

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