Pro-government fighters recaptured a provincial capital Sunday in southern Yemen after three days of intense fighting against Shiite rebels and their allies, military officials said, the latest in a string of battlefield successes by the Saudi-backed troops.

The recapture of Zinjibar, the capital of Abyan province, came one day after a friendly fire incident in which a Saudi-led coalition airstrike hit the pro-government fighters while traveling on a coastal road toward Zinjibar, killing at least 20, officials said.

The Saudi-led, American-supported coalition began launching airstrikes in March against Shiite Houthi rebels and their allies — troops loyal to former President Ali Abdullah Saleh — who control the capital, Sanaa, and much of northern Yemen. They are pitted against southern separatists, local and tribal militias, Sunni Islamic militants and loyalists of exiled President Abed Rabbo Mansour Hadi.

The military officials said the battle for Zinjibar saw the deployment of modern tanks and fighting vehicles, which have significantly strengthened the pro-government troops.

The tanks and vehicles are widely thought to have been supplied by Saudi Arabia and the United Arab Emirates. Neither country has publicly acknowledged sending forces there.

However, the United Arab Emirates said Saturday that three of its soldiers were killed while taking part in the Saudi-led campaign. A statement carried by the official news agency WAM did not say how or where the soldiers were killed. The latest deaths take to five the number of Emirati soldiers killed in battle since March.

Yemeni security officials have said that Saudi, Emirati, Egyptian and Jordanian military advisers are training hundreds of fighters at a military base near Aden.

All officials spoke on condition of anonymity because they were not authorized to speak to journalists.