ADEN, Yemen — Houthi fighters and Saudi-backed pro-government forces renewed fighting in Yemen’s port city of Hodeidah on Wednesday.

The fighting breached a cease-fire and is likely to complicate a troop withdrawal agreement intended to pave the way for wider peace talks aimed at ending the four-year war, which is seen as part of a wider regional conflict between Saudi Arabia and the Iran-backed Houthi.

Tens of thousands of people have been killed, many of them civilians, and aid agencies say the humanitarian crisis is the worst in the world.

As the main entry point for food imports and aid, Hodeidah, which has been under Houthi control, is a lifeline for millions of Yemenis threatened by starvation because of the war.