Yemen’s government troops have been battling Houthi rebels for a third day in the capital Sanaa after the collapse of ceasefire talks, officials and residents say.

Explosions were heard on Saturday near the Interior Ministry in the northern part of Sanaa, a day after the Shia fighters began shelling the state television building as they advanced into the city.

Khaled Hammadi, a journalist based in Sanaa, told Al Jazeera that heavy smoke was hanging over the area of the state TV building on Saturday.

“Fighting is expanding hour by hour and the Houthi rebel fighters are advancing into neighbourhoods near important areas,” he said.

Meanwhile, reports from Sanaa said the Yemeni army was commencing a counterattack on the Houthis with back-up from the Republican Guard unit.

Thousands of Houthis have been staging protests in Sanaa for more than a month now, besieging ministries and blocking the road to the main airport.

Fighting in Sanaa had become so intense that by Friday international airlines suspended flights in and out of the nearby airport.

The UN has failed to mediate a peace deal between the warring sides.

Jamal Benomar, the UN envoy to Yemen, left the northern city of Saada on Friday after trying to mediate a deal that could pave the way for a new government and more political representation for the Houthis.

Clashes have raged on the outskirts of Sanaa for days, with dozens of deaths reported.

Earlier, Al Jazeera’s Hashem Ahelbarra, reporting from Sanaa, said the country “is just a few hours” from plunging into a civil war as the capital is divided along sectarian lines, with one half run by Sunnis and the other by Houthis”.

“The Houthis have control over most of the north of the country – from Saada to the gates of Sanaa,” he said.

“They have thousands of fighters and some military commanders and members of the former regime with them. And if in the coming hours they decide to control Sanaa, they can definitely control the capital.

“If the Sunnis decide to join the fight against the Houthis, it’s definitely going to be civil war in the country […] It’s either peace or war.”

The Houthis are a Zaidi Shia group whose traditional power base is in the north. They are demanding a new government and also more political power for their community.

The government’s plans for a six-region federation in Yemen has been rejected by both the Houthis and the southern separatists. Al Jazeeera