Smoke billows from a military arms depot after it was hit by a Saudi-led air strike on the Nuqom Mountain overlooking Yemen's capital Sanaa June 1, 2015. [Photo/Agencies]

SANAA - Efforts to coax Yemen's warring factions into talks have made some progress, officials said on Monday, as warplanes from a Saudi-led coalition mounted more air strikes on the country's dominant Houthi militia.

An Arab alliance has been bombing the Houthis since March 26 in a bid to restore exiled President Abd-Rabbu Mansour Hadi to power. The Sunni Muslim states regard the Houthis as a threat to the stability of Yemen, which flanks the world's top oil exporter Saudi Arabia.

Political sources in Oman confirmed on Monday that diplomats were brokering talks between US and Houthi envoys in the capital Muscat aimed at finding a peaceful resolution to a conflict that has killed over 2,000 people since March.

Oman added on Monday that it had located two missing foreign citizens - an American and a Singaporean -- in Yemen who were reported in Arab media on Sunday as being held by Houthis, and evacuated them to Muscat after coordination with "the relevant authorities in Yemen", the state news agency said.

Three more US citizens, two of Yemeni and one of Somali origin, are in Houthi custody, said an official in Sanaa, now controlled by the Houthis and allies of ex-president Ali Abdullah Saleh.

Independent politicians in Sanaa said the new diplomacy had succeeded in narrowing gaps between the Houthis and the exiled government to pave the way for eventual United Nations-backed negotiations in Geneva.

"There's progress in the talks toward an agreement on a long truce and reviving political dialogue," one politician told Reuters, speaking on condition of anonymity.