Yemen’s Huthi rebels have seized control of a strategic city north of the capital, government officials said Sunday, a victory analysts say could change the course of the five-year-old war.

The Iran-aligned militia captured Al-Hazm, capital of the northern province of Al-Jawf, enabling the rebels to threaten the oil-rich neighbouring province of Marib, a government military official told AFP.

“The Huthi rebels have taken control of Al-Hazm, the regional capital of Al-Jawf, after fierce fighting with government troops who were forced to withdraw” to Marib, he said.

“Most of Al-Jawf is under Huthi control.”

According to other military sources, at least 30 government troops—including high-ranking officers—were killed in fighting over the past two days.

The Huthis also suffered dozens of casualties, the sources added.

Al-Jawf was already mostly controlled by the Huthis, but its capital—only 150 kilometres (90 miles) south of the border with Saudi Arabia—had been in loyalist hands.

Yemen’s internationally-recognised government has been battling the Huthi rebels since 2014 when they captured the capital Sanaa and swathes of the impoverished Arab nation.

The government has been backed by a Saudi-led military coalition since 2015.

Mohammed Ali al-Huthi, a leading figure in the rebels’ political wing, congratulated their forces on Twitter.

“We congratulate (Huthi forces) on their victories and we congratulate the steadfast Yemeni people for crushing the invaders and their mercenaries in Al-Jawf,” he said, referring to the Saudi-led coalition and government forces.

Maged al-Madhaji, executive director of the Sanaa Centre, a Yemeni think-tank, said the Huthis’ capture of Al-Hazm could be a game-changer.

“Control of the capital of Al-Jawf could totally change the course of the war. Huthis have made an exceptional advance and are changing the balance” in their favour, Madhaji told AFP.

He said the advance would enable the rebels to surround Marib, the most significant territory government hands.

It also secures supply lines between Sanaa and the Huthi northern stronghold of Saada, Madhaji said.

Since the Saudi-led coalition intervened in March 2015, tens of thousands of people, mostly civilians, have been killed and millions displaced, in what the UN has termed the world’s worst humanitarian crisis.