Hudaida, Yemen's main port and a lifeline for millions of Yemenis on the brink of starvation, became the focus when the Saudi-led coalition tried twice to seize the port to cut off the Houthis' main supply line.
Yemen's warring parties have set up joint frontline observation posts in the flashpoint port city of Hudaida, the United Nations said on Wednesday, the latest step in UN efforts to maintain a ceasefire in the Red Sea port city.
A ceasefire and troop redeployment agreement for Hudaida was reached at December peace talks in Sweden as a trust-building measure to pave the way for wider talks to end the war.
The tentative ceasefire has reduced, but not stopped, violence, and the troop withdrawal stalled for many months before a pull-out by Iran-aligned Houthi forces from three Red Sea ports in May under phase one of the deal.
A Western-backed, Sunni Muslim coalition led by Saudi Arabia intervened in Yemen in March 2015 after the Houthis ousted the internationally recognised government from power in Sanaa in late 2014.
Hudaida, Yemen's main port and a lifeline for millions of Yemenis on the brink of starvation, became the focus of the more than four-year conflict last year when the coalition tried twice to seize the port to cut off the Houthis' main supply line.
The head of the United Nations' Hudaida mission, Abhijit Guha, welcomed the establishment of the four observation posts, which aim to "facilitate direct inter-party de-escalation," said a UN statement.
"The two parties finalised written agreements in all four locations and deployed liaison officers at each observation post," it said.
Guha called on all parties to reduce rhetoric and support the efforts to maintain the ceasefire in Hudaida.