Sanaa, Feb 10 (IANS): Two massive explosions struck Yemen's Marib, as violence has continued in the government-controlled oil-rich northeastern city, a government official said.

"Two massive explosions caused by ballistic missiles fired by the Houthi rebels against the densely populated city of Marib, with no casualties," the official told Xinhua news agency on Tuesday.

The two Houthi-fired ballistic missiles landed on an empty area near a government facility in Marib, he added.

For the third consecutive day, the southern and western areas of Marib are witnessing non-stop battles, leaving dozens from the two-warring sides dead and injured.

"Nearly 30 soldiers were critically injured in today's fighting and are receiving treatment at the medical centre," sources at Marib's public hospital said.

In the past two days, the Iran-backed Houthi rebels intensified their military operations and carried out a large offensive against the city controlled by the Yemeni government.

Earlier in the day, UN Special Envoy for Yemen Martin Griffiths expressed concern over renewed attacks.

"Extremely concerned about the resumption of hostilities in the governorate of Marib by Ansar Allah (Houthi rebel group), especially at a time of renewed diplomatic momentum to end the war in Yemen and resume the political process," Griffiths tweeted.

"A negotiated political settlement that meets the aspirations of the Yemeni people is the only sustainable solution to end this conflict," the UN envoy noted.

Yemen has been mired in a civil war since late 2014, when the Houthi militia seized control over several northern provinces and forced the internationally-recognized government of President Abd-Rabbu Mansour Hadi out of the capital Sanaa.