People gather on the rubble of shops destroyed by a Saudi-led airstrike at a market in Sanaa.
Sanaa - The rebels and their allies started shelling the town of Dar Saad on Sunday, after losing control of some of Aden's neighbourhoods.
The death toll in Yemen from the Houthi rebel shelling of a town near the southern port city of Aden rose on Monday to nearly 100, the head of an international aid group said, describing it as "the worst day" for the city and its surroundings in over three months of fighting.
The rebels and their allies started shelling the town of Dar Saad on Sunday, after losing control of some of Aden's neighbourhoods. The violence highlighted the bloody chaos of the civil war gripping the Arab world's poorest country, which also has been the target of Saudi-led, US-backed airstrikes since late March.
Hassan Boucenine of the Geneva-based Medicins Sans Frontieres, or Doctors Without Borders, said that by Monday, his organisation reported nearly 100 people dead, twice the casualty toll from the previous day.
The shelling also left about 200 people wounded, said Boucenine, the head of MSF in Yemen. Of the victims, 80 per cent are civilians, including many pregnant women, elderly and children, he added.
"Yesterday was the worst day in Aden since (the Saudi-led coalition campaign) started in March," Boucenine said, adding that he fears "attacks on civilians will continue."
Sunday's shelling in Dar Saad began after the Houthi rebels lost control of much of the Aden district of Tawahi, according to officials and witnesses. Tawahi is now under a security lockdown, the officials said, as anti-Houthi forces search buildings looking for rebels, some of whom had fled to the nearby mountains.
Overnight, the Saudi-led coalition targeted Houthi positions north of Aden and in Dar Saad, killing at least 55 rebels, the officials and witnesses said.
The coalition also struck the home of Mehdi Meqlawa, a prominent supporter of former President Ali Abdullah Saleh, in a Sanaa suburb. In the Yemeni capital, it hit Houthi headquarters near the Souq Aziz market, killing one person.
Rebel shelling continued on Monday in the city of Taiz, Yemen's third largest, killing eight residents there, while ground fighting raged on in Marib, with six anti-Houthi tribesmen and 10 Houthi fighters killed in the clashes. All officials and eyewitnesses spoke on condition of anonymity because they were not authorized to talk to reporters.
Houthi officials declined to comment on the fighting.
A Yemeni man carrying his daughter looks at a building destroyed during fighting against Houthi fighters in the port city of Aden.