Six Saudis detained by Yemen's Huthi rebels were released and flown to Riyadh on Wednesday, officials said, as efforts to end the five-year conflict gain momentum.

The release, overseen by the International Committee of the Red Cross (ICRC), comes after 128 Huthi rebels detained in Saudi Arabia were freed and repatriated to Sanaa in November.

"We are happy to see a momentum occurring with the release of detainees that has been happening on both sides," said Freya Raddi, ICRC's deputy head of delegation in Yemen.

"Today is important as six more families will be reunited. It is a special moment when this happens, and we are honoured to be part of it."

The Saudi-led military coalition fighting the rebels confirmed the six "prisoners of war" had arrived at Riyadh's King Salman airbase on Wednesday, Saudi state media reported.

It was unclear when and under what circumstances the Saudis were detained.

The Huthi-run Al-Masirah television said the rebels had handed over the prisoners to the ICRC, adding that they were waiting for the coalition to reciprocate by releasing "our prisoners".

The Huthis freed by Riyadh in November had been captured in various parts of Yemen between 2015 and earlier this year.

The initiatives coincide with a lull in Huthi attacks on Saudi Arabia and come after a senior official in Riyadh recently said it had an "open channel" with the Iran-backed rebels.

Riyadh and its allies intervened in the Yemen war in March 2015 to support the internationally recognised government, shortly after the Huthis seized Sanaa.

Since then, tens of thousands of people have been killed and millions displaced by Yemen's conflict, which the UN has termed the world's worst humanitarian crisis.