Yemen's President Abd-Rabbu Mansour Hadi has returned to the Saudi capital Riyadh after routine medical treatment in the United States, according to his Twitter account on Wednesday.

He had left for the United States last month for medical treatment, Reuters had reported on August 11, citing two sources close to the matter.

The head of the country's internationally-recognised government, who has lived in exile in Riyadh since the Iranian-aligned Huthi group captured the Yemeni capital Sanaa in 2015, has been treated for a heart condition since 2011.

Yemen's conflict has killed more than 100,000 people since a Saudi-led alliance intervened in Yemen in March 2015 to try to restore Hadi's government, an ally of Riyadh. The war is largely seen regionally as a proxy struggle between Riyadh and Tehran.