The highest leader of Yemen's Houthi insurgency, Abdul-Malik Badreddin al-Houthi, on Sunday urged the rebels and the tribes loyal to the movement to defend the port city of Al Hudaydah, where forces loyal to Yemeni President Abdrabbuh Mansour Hadi are preparing to break through.

The army and the tribes must continue and go towards the province of Al Hudaydah to reinforce the military situation, the leader said in a speech.

Government troops and allied militias, which have the support of the Saudi-led coalition, are now in an area about 18 kilometers south of Al-Hudaydah port, in the west of the country, and on the main supply route to the rebel-held enclaves.

"Our country is threatened, and it is everyone's responsibility, with all religious, patriotic, humanitarian and nationalist considerations, to move and face this aggression," al-Houthi added, warning his followers not to hesitate and encouraging them to act together.

In his speech, the leader also described the latest progress of the forces loyal to President Hadi as "limited," saying that they are "mercenaries" and "the shoes" for the feet of Saudi Arabia, the United Arab Emirates and the United States.

The United Nations has called on the Arab coalition, which operates in Yemen against the Houthis, to avoid attacking Al Hudaydah port, as two thirds of Yemen's population are suffering food insecurity and 70 percent of those affected rely on supplies arriving through that port.

Yemen has been the scene of a brutal civil war since late 2014, when the rebels took the capital, Sana'a, as well as provinces in the north and west of the country and deposed the government in Sana'a.

The central administration currently has its headquarters in the southern city of Aden, while President Hadi is in exile in Riyadh, Saudi Arabia.

The conflict exacerbated in March 2015, with the intervention of the US-backed Arab coalition.