An international charity says fighting in two Yemeni provinces has killed at least 350 civilians in the past three months.

The Norwegian Refugee Council said Monday that civilian deaths have doubled in Hajjah and Taiz provinces, even as casualties in the flashpoint city of Hodeida were down since a shaky ceasefire came into effect there in December.

Mohamed Abdi, NRC director in Yemen, says "fighting is intensifying in other parts of the country with a devastating impact on civilians," citing 164 people killed in Hajjah and 184 in Taiz.

The NRC's analysis found that while civilian casualties from airstrikes were down by half since December, attacks from roadside bombs, mines and snipers were on the rise.

Yemen's civil war, which erupted in 2014, pits Houthi rebels against the Saudi-backed government.