Heavy fighting in Yemen's Taiz

Heavy clashes and airstrikes in Yemen's third city Taiz left at least 36 fighters dead on Sunday, army sources said, as aid workers struggled to make medical deliveries.

The fighting between Saudi-backed pro-government forces and Houthi rebels killed at least 21 rebels and 15 loyalists, the sources said.

New clashes broke out when loyalist forces tried to take back a presidential palace on a hill overlooking the city's east.

Fighting has left Taiz in a desperate situation, with closed hospitals and acute shortages of medicine, food, water and fuel - Red Cross

Loyalists control the centre of Taiz, encircled by the Houthi rebels and allied forces loyal to ousted president Ali Abdullah Saleh.

The city in central Yemen has been a key battleground as forces loyal to President Abedrabbo Mansour Hadi seek to regain ground from the Houthis.

In a statement on Sunday, aid group Doctors Without Borders [MSF] said essential medical supplies it hoped to deliver to a besieged enclave of the city were being blocked.

"It is very frustrating that, after weeks of negotiations, we have made no progress in convincing officials of the need to provide impartial medical assistance to the victims of the ongoing fighting within this enclave," Karline Kleijer, MSF's emergency manager for Yemen, said.

She said that this was despite MSF's support to health facilities in Houthi-controlled areas.

Only six of 20 hospitals in the city of more than 600,000 continue to function due to the conflict, and often only partially, MSF said.

"They lack staff, fuel and essential medicines, and are overwhelmed by the high numbers of wounded seeking to access their emergency services on a daily basis," it said.

Intensifying fighting has left Taiz in a desperate situation, with closed hospitals and acute shortages of medicine, food, water and fuel, the Red Cross said this week.

The Houthis overran Yemen's capital Sanaa in September 2014 and went on to seize control of several regions, aided by Saleh's forces.

In July, loyalists backed by the Saudi-led coalition evicted the rebels from five southern provinces and have set their sights on Sanaa.

At least 4,500 civilians have been killed in the conflict since March, when the coalition began targeting the rebels in airstrikes.

Telesur a pan-Latin American television network also revealed yesterday that up to 800 Colombian nationals, including former Colombian soldiers, could soon be fighting in Yemen under contract with Saudi Arabia.

The network, that is headquartered in Venzuela, said dozens of Colombians were already likely to be fighting in the war-torn country. 

Colombian newspaper El Tiempo reported that just under 100 Colombian troops arrived in Yemen earlier this month, according to Telesur.