A suicide bomber killed at least four people Tuesday in Yemen's southern port city of Aden, as a cease-fire between pro-government forces and Houthi rebels stretched into a second day with some reports of fighting.
The attacker detonated the explosives among a group of army recruits in the city that has become home to the government since it pushed out the Houthis with the help of a Saudi-led coalition.
But the instability in Yemen has also brought al-Qaida militants seeking control in parts of Aden.
The United Nations is sponsoring peace talks next week between the government and Houthis and urged them to make sure their cessation of hostilities holds in order to create a good environment for the negotiations.
The Houthis seized control of the Yemeni capital, Sana'a, in September 2014, but the conflict exploded into a regional fight in March of last year when the rebels marched on Aden and forced President Abdu Rabu Mansour Hadi to flee to Saudi Arabia.
The Saudis responded by organizing a coalition of militaries to conduct airstrikes in Hadi's defense and later expanded the effort to include ground troops.
A U.N. spokesman said Monday there were "pockets of violence" after the truce went into effect. Much of the reported fighting was in the city of Taiz.
More than 6,200 people have been killed in the Yemen conflict, and the U.N. said more than 80 percent of civilians are in desperate need of food and medical aid.
With the cease-fire in effect, the U.N. is conducting a three-day polio vaccination campaign in Yemen that began Monday with a target of reaching 5 million children.