The Saudi-led coalition fighting against the Houthi rebels in Yemen said early on Thursday that air strikes were launched on military targets in the Yemeni capital, Sanaa, and the north-western city of Saada.

A weapons depot and one of the main Houthi supply lines in Sanaa were among the targets of the strikes, the coalition said in a statement reported by state news agency SPA.

The coalition also said it destroyed Houthi workshops in Saada where ballistic missiles and drones were assembled.

The Houthis have repeatedly launched cross-border attacks on Saudi Arabia using drones and missiles.

The coalition, which intervened in Yemen in March 2015 after the Iran-backed rebels seized the capital, has increased strikes on Houthi sites in Sanaa in recent days.

On Wednesday, the coalition said it destroyed an explosive-laden boat launched by the Houthis from Hodeidah on Yemen's Red Sea coast.

The coalition had earlier destroyed a drone that took off from Sanaa airport.

On Tuesday, it said it launched a strike on a site that belonged to Iran's Islamic Revolutionary Guard Corps.

The coalition has told civilians not to gather at or approach potential targets.

Meanwhile, battles between government forces and the rebels have intensified in the northern city of Marib. The fighting has forced large numbers of people to flee to makeshift desert camps.

The city is the last northern bastion of the internationally recognised Yemeni government. Marib, about 170 kilometres east of Sanaa, is at a crossroads between the southern and northern regions of the country and includes a motorway to Saudi Arabia.

Marib province has oil and gasfields, making it a major economic prize.