Forces loyal to Yemen's exiled government say they have advanced into the last part of the southern city of Aden still held by Houthi rebels.

A spokesman said on Monday that local militias and army units, backed by Saudi-led coalition air strikes, had taken most of the Tawahi district.

On Friday, the government declared that the city had been "liberated" after four months of fierce fighting.

Clashes continued over the weekend, however, leaving dozens of people dead.

On Sunday, rebel artillery fire struck the densely-populated northern suburb of Dar Saad, where many displaced people live, Medecins Sans Frontieres (MSF) said.

The medical charity said its hospital in the area received 150 casualties, among them women, children and elderly people. Forty-two people were dead on arrival and tens of other bodies had to be turned away because the hospital was overwhelmed.

MSF added that it had witnessed "massive retaliation against civilians by the Houthis" and warned that it feared targeted killings of civilian populations would recur in the south of Yemen as the rebels were driven out of areas they control.

The Houthis denied targeting civilians in Dar Saad and blamed "media deception".
'Flushing out'

Fighters from the Popular Resistance Committees (PRC) and soldiers advanced into Tawahi, at the western tip of the Aden peninsula, late on Sunday after securing the neighbouring Crater district, militia spokesman Ali al-Ahmedi said.

Why is there fighting in Yemen?

Northern Shia Muslim rebels known as Houthis, backed by forces loyal to Yemen's ex-president, took over parts of Yemen, including Sanaa, and forced the government into exile in March
The rebels accused the government of corruption and of planning to marginalise their heartland within a proposed federal system
Forces loyal to the government, and southern militia, are fighting back, aided by air strikes led by neighbouring Saudi Arabia

Yemen crisis: Who is fighting whom?

They took control of state television and radio buildings, as well as military and security facilities.

An operation was currently under way to "flush out" the remaining rebels, Mr Ahmedi told the AFP news agency, adding that some had taken positions on rooftops.

Fighting was also reported on Monday around key military bases to the north and east of Aden, in the provinces of Lahj and Abyan, and in the central city of Taiz, according to the Reuters news agency.

The Houthis and allied security forces loyal to ousted former President Ali Abdullah Saleh have vowed to resist the offensive.

The losses in Aden represent the biggest setback for the rebels since the Saudi-led air campaign against them started on 26 March, a day after they entered the city.

Mr Hadi had taken refuge there the previous month after the Houthis consolidated their control of the capital, Sanaa, and placed him under effective house arrest.

In a separate development on Sunday, at least 20 civilians were killed in coalition air strikes in the Houthis' northern stronghold of Saada province, the rebel-controlled Saba news agency reported.

The UN says more than 3,200 people, half of them civilians, have been killed in air strikes and fighting on the ground in the past 16 weeks.

Another one million civilians have been displaced by the conflict and more than 80% of Yemen's 25 million people now need some form of humanitarian aid.