Fighting broke out north of Yemen's capital and in the center of the country on Sunday, killing more than 20 people, hours before a planned halt to the fighting aimed at facilitating talks to end the year-long war.

Yemen's government and its Iran-allied Houthi enemies are supposed to implement the U.N.-backed "cessation of hostilities" from midnight (2100 GMT) before peace negotiations begin in Kuwait on April 18.

The United Nations hopes this will lead to a more concrete, formal cease-fire with peace-building steps.

The war has killed more than 6,200 people, drawn in rival regional powers Saudi Arabia and Iran and tipped one of the Arab world's poorest countries into a humanitarian crisis.

But hours before the planned halt in fighting, heavy battles flared between forces loyal to Yemen's President Abd-Rabbu Mansour Hadi and Houthi fighters in al-Maton, a town north of the capital Sanaa, killing and wounding several fighters, local residents said, without giving precise figures.

In the central Bayda province, battles between the rival forces in al-Sawadiya and al-Zaher districts killed more than 20 people, local officials and residents said, and fighting continued in the southwestern city of Taiz.

Hadi, whose forces are backed by a Saudi-led military coalition which has been carrying out airstrikes on Yemen for the past year, met his advisers in Riyadh on Sunday to discuss the impending halt in fighting, Yemeni officials said.