A 48-hour truce aimed at ending Yemen's civil war came under pressure today as residents said fighting was still going on in parts of the country.

The ceasefire declared by the Saudi-led military coalition trying to restore a Saudi-backed government raised hopes of an end to a 20-month conflict that has drawn in regional rivals Iran and Saudi Arabia and left Yemen on the verge of famine.

It appeared largely to be holding today but was strained by gun battles in the key western city of Taiz, and by air strikes by the Saudi-led coalition reported by residents in villages east of the capital Sanaa.

A Saudi general accused the Houthis, the Shi'ite militia that controls Sanaa, of launching a ballistic missile, in violation of the ceasefire.

The missile was fired into the eastern desert province of Marib, Brigadier General Ahmed al-Assiri told Saudi-owned al-Hadath TV.

"Perhaps on the second day of the truce we will witness a sense of responsibility, otherwise the situation will be dealt with proportionately," Brigadier General Assiri said.

Brigadier General Sharaf Luqman, a spokesman for the Yemeni armed forces allied with the Houthis, said the movement remained committed to a cessation of hostilities but was ready to "defend Yemen's independence in the event of continuing aggression".

Siege of Taiz

Yemen's Saudi-backed government, led by President Abd Rabbu Mansour al-Hadi, and the Iranian-aligned Houthis blamed each other for the fighting in mountainous Taiz, where thousands of civilians are trapped and many have been wounded.

Government forces this week made advances on Taiz, threatening to break a year-long Houthi siege.

Saudi Arabia and allied Sunni Muslim Gulf states began a military campaign in March last year to prevent the Houthis and forces loyal to ex-president Ali Abdullah Saleh taking control of the whole country.

The Saudi-led coalition expelled enemy fighters from the southern port city of Aden last summer but the Houthis continue to hold swathes of territory including the capital, with help from Saleh loyalists.

More than 10,000 Yemenis have been killed in the war.