International airlines have suspended flights to Yemen's capital as fighting between rebels seeking greater political clout and Islamists backed by the army encroaches on the country's main airport, authorities said.
Yemeni television's three channels stopped transmitting on Friday after the state broadcaster's studios in the Jraf area near the airport came under fierce fire overnight, an official there said.
The northern area of the capital Sanaa where the airport is located was the scene of fierce clashes on Thursday in which nearly 40 people on both sides were killed, according to various sources.
The Shiite rebels, known as Huthis or Ansarullah, appear more determined than ever to step up military pressure on Sanaa to secure their demands: a new government and more power for their community.
The Civil Aviation Authority, in a statement issued overnight, said international airlines had suspended flights to Sanaa for 24 hours because of the latest violence.
But Turkish and Jordanian aircraft that were already en route before the suspension came into effect were able to land at night and leave again, the official Saba news agency reported.
"Arab and foreign airlines have decided to suspend their flights to Sanaa for 24 hours because of developments in the capital," said the statement carried by Saba.
The move, which could be extended or reconsidered depending on the security situation, came as UN envoy Jamal Benomar held talks in the rebel bastion of Saada to try to resolve the crisis.
The rebels, who have been camped north of Sanaa for weeks, belong to the Zaidi Shiite community, a minority in mainly Sunni Yemen but a majority in the northern highlands.
They have battled the government for years from their heartland of Saada in the remote north, complaining of marginalisation since the rule of now toppled autocratic president Ali Abdullah Saleh.
This week, they rejected an offer from President Abdrabuh Mansur Hadi to name a new prime minister and reduce a controversial fuel price rise, two of their core demands.
Analysts say the rebels are trying to establish themselves as the main political force in the region.
The wave of violence intensified Thursday with the advance of rebels on Shamlan suburb north of the capital, and through the night on a Thalathin Street linking the area to Imam University, which is run by Sunni fundamentalists.
The fighting then spread to offices of Yemen's state television, which was hit by mortar fire.
On Friday its three channels were off the air.
"Transmissions have ceased because of incessant fire from Huthis since Thursday evening," an official at the broadcaster said.
The authorities said the rebels managed to advance and "take control of positions of the security forces and the army at Shamlan" and along Thalathin Street.
The country's high security commission warned the Shiite rebels to withdraw, with a spokesman quoted on Saba as saying that "legal action... will be take to recapture these positions".
Early on Friday, residents said government forces managed to reclaim some of the positions they lost earlier.
Meanwhile, Benomar tried to convince Ansarullah leader Abdelmalek al-Huthi to ease the crisis, sources close to the negotiations said, although he was unable to make any headway.
"Mr Benomar had more discussions late into the night with Abdelmalek al-Huthi, but without any result," one source told AFP on Friday.
Representatives of President Hadi were also holding separate talks with Huthi in Saada, where Benomar has been overseeing negotiations since Wednesday.
Those attending the ongoing talks were eager to secure an agreement in Saada on Friday, "with or without" Huthi's backing, the source added.
Hadi has already agreed to involve the rebels in the formation of a new government to replace the unpopular administration which imposed austerity measures, including a fuel price hike, earlier this year.
But the rebels are also demanding positions in key state institutions.
The crisis has exacerbated an already difficult transition since Saleh's ouster, which has also seen mounting secessionist sentiment in the formerly independent south and persistent attacks on the security forces by Al-Qaeda.