Just hours after the U.N.-mediated ceasefire came into effect, there were reports of Saudi-led airstrikes in Sana and ground fighting in the southern city of Taiz.
Both sides blame each other for the attacks.
Speaking Tuesday at the begining of peace talks in Switzerland, U.N. Special Envoy to Yemen appealed for compromise.
Yemen is being eaten up by fire from all sides as a result of the violence and the armed conflict in the country. And here we repeat again: the only solution is a political solution, and the violence must stop.
For months Yemen has been spiraling toward all out civil war between Iran-backed Houthi rebels and forces loyal to the president.
A Saudi-led coalition of Gulf Arab forces, aided by the United States, has been carrying out strikes against the Houthis since March.
Nearly 6,000 people have been killed in the fighting. Doctor Ahmed Shadoul of the World Health Organization said the humanitarian situation was catastrophic, with civilians living under a state of siege.
Unfortunately about 2.5 million displaced who have been around in different areas in not a well prepared living situation, and this in itself, is a high risk area of mosquito breeding, of outbreaks of malaria, outbreaks of dengue.
Human rights groups have accused the Saudi-led coalition of attacking civilian targets. Riyadh, and its backers, deny targeting civilians.
Amnesty International says at least five airstrikes since August have struck schools.
Six-thousand-five-hundred children were attending these schools. And all of them have had their education severely disrupted as a result. Schools should be a safe space for children and for civilian life. In some of these cases these schools were targeted more than once and struck on repeated days.
Saudi Arabia has not responded to Amnesty's allegations.
The peace talks are due to last a week, but rivals on the ground are not disarming.
Yemen's prime minister claimed Wednesday several of what he called "resistance" groups are being merged into one unified force to take on the Houthis.