At least 12 civilians have been killed in Yemen's southern city of Taiz as Houthi fighters continued their offensive on the penultimate day of a fragile humanitarian ceasefire.

Government officials said on Saturday that another 51 people were wounded after the rebels shelled several neighbourhoods in the city's Hawd Al Shraf and Shamasi districts.

Some 26 fighters loyal to the Houthis and former president Ali Abdullah Saleh and 14 loyalists of President Abd-Rabbu Mansour Hadi were also killed.

Meanwhile, in the southern province of Ad-Dali', five Houthis were killed overnight when their convoy was ambushed; and in the coastal city of Aden, heavy artillery, including tank shells, fell on the city's northern sector and west.

The Houthis had indicated they would abide by the ceasefire, which was proposed by Saudi Arabia and backed by the US in order to allow aid into the stricken country.

On Friday, the first of six planes carrying humanitarian aid landed in the capital, Sanaa. The plane was carrying 25 tons of aid, including blankets, kitchen utensils, sleeping mats and medicine.

The Houthi-run Saba news agency said fuel shipments were being distributed across the country.

Yemen is mired in a humanitarian catastrophe, as 300,000 people have been displaced by the conflict and 12 million are short of food.

The conflict pits Houthi rebels, who are fighting for control of Yemen, against forces loyal to Hadi, who was forced to flee to Saudi Arabia.

Saudi Arabia leads a military coalition involving Arab countries and major powers, including the US, which launched air strikes on rebel positions on April 26. 

Source: Al Jazeera and agencies