At least 40 people have been killed in clashes between Yemeni army troops and gunmen affiliated with the Shiite Houthi militant group since Thursday in the northern province of Al-Jawf, a local official said.

Over Friday night, as many as 30 Houthi militants, who are fighting for control of roads linking Sanaa with the oil production province of Marib, were killed in clashes with army troops, backed by armed tribesman, the official told Anadolu Agency.

The latest round of fighting in the province north of Sanaa comes as thousands of Houthi supporters have been staging massive protests in the capital for the last several weeks to demand the dismissal of the government and the reversal of an earlier government decision to slash fuel subsidies.

On Friday, supporters of the Yemeni government and its opponents held huge rival rallies Friday in Sanaa, where tensions escalated as Shiite Houthi rebels vowed to step up anti-government protests.

Tens of thousands of Shiite rebels, also known as Zaidis or Ansarullah, gathered with supporters for the weekly Friday prayers along the airport road, where they have been demonstrating for weeks.

After the prayers, organisers called for further action against the government, which the Houthis accuse of corruption and whose resignation they have been demanding.

The Shiite rebels have rejected overtures from President Abdrabuh Mansur Hadi to name a new prime minister, replace the government and reduce a disputed fuel price hike.

Taha al-Mutawakel, a member of Ansarullah's politburo, called for "civil disobedience" and urged supporters to join in new protests on Sunday and Monday to keep up the pressure on the government.

"People want escalation," protesters chanted, according to an AFP correspondent.

At the same time, supporters of the embattled government mobilised what appeared to be a much larger crowd for a rival rally and prayers on Sittin Street in western Sanaa.

The protesters chanted slogans of support for Hadi and denounced Houthi protests that have crippled the capital, an AFP correspondent reported.

"Listen to us Houthi: The Yemeni people believe in the republic," they chanted.

The official Saba news agency said "millions" of Hadi supporters took to the streets in Sanaa and in other parts of Yemen on Friday.

The rebels, who have been camped inside and outside Sanaa for weeks, have dismissed as insufficient the 30 percent cut in the fuel price hike and pressed demands to end alleged corruption.

They have threatened to escalate their campaign against the government, which included briefly blocking main arteries in Sanaa on Wednesday.

Yemen has been locked in a protracted transition since long-time president Ali Abdullah Saleh was forced from power in February 2012 after a deadly 11-month uprising.