Yemeni pro-government forces have advanced to within 40 kilometres (25 miles) of Sanaa in a push towards the rebel-held capital from the northeast, loyalist military sources said on Friday.

Loyalist forces took the town of Nihm after overrunning the headquarters of the renegade pro-rebel 312th Brigade of the army earlier this week, the sources said.

The advance puts them within striking distance of the heights overlooking Sanaa international airport, where residents said the rebels were digging trenches and laying minefields.

Both sides suffered losses in the battle for the camp.

"We are now on the road to Sanaa," said a jubilant loyalist fighter who gave his name only as Mohammed.

"We ask our brothers, the fighters of the national army, to be patient. Victory will be at hand very soon."

The push towards Sanaa from the east comes with loyalist forces making little headway in their efforts to advance into central Yemen from their stronghold in the south.

Since a Saudi-led coalition intervened in support of President Abedrabbo Mansour Hadi last March, his loyalists have ousted Shia Huthi rebels from five southern provinces.

But in the north they have been largely confined to Marib, east of Sanaa, and Jawf, on the Saudi border.

Progress has been slow, partly because of Yemen's mountainous terrain and in part because of the determined support the rebels have received from army units still loyal to Hadi's predecessor, Ali Abdullah Saleh.

The United Nations says the conflict has claimed more than 6,100 lives, nearly half of them civilians.