The Swedish diplomat, who took up the post in September, made the comments during a visit to Taez in the war-torn country's southwest.

As he wrapped up talks with Taez's governor and other political leaders, the coalition claimed another heavy death toll among rebels fighting to seize Marib in the north.

As well as 115 Huthis killed, 19 rebel vehicles were destroyed in coalition strikes over the past 24 hours in Sirwah, west of Marib city, and Al-Jawf to the north, it said in a statement carried by the official Saudi news agency SPA.

Grundberg said "military operations (are) causing significant casualties, which are exacerbating the humanitarian situation and undermining peace efforts".

"Working for peace in Yemen is an uphill battle," he added, while holding out hope of a breakthrough.

"We should never forget that there is always a way to break the cycle of violence. There are always opportunities for peaceful dialogue."

- US diplomat visits -

In another diplomatic initiative, US special envoy Tom Lenderking, appointed by President Joe Biden to seek an end to the war, made his first visit to Yemen with a stop in Aden, the government's stronghold.

Lenderking, who met Prime Minister Maeen Abdulmalek Saeed, called for better coordination with southern separatists who have also periodically clashed in recent years with the Saudi-backed government.

Lenderking stressed "that now is the time for all Yemenis to come together to end this war and enact bold reforms to revive the economy, counter corruption and alleviate suffering", State Department spokesman Ned Price said in a statement.

"Division weakens all parties and only exacerbates suffering," Price said.

Members of the separatist Southern Transitional Council were integrated into the cabinet in December 2020 but the power-sharing arrangement remains shaky.

Lenderking travelled to Aden with Cathy Westley, who is the top diplomat at the US embassy for Yemen but is based in Riyadh for security reasons.

The Saudi-led coalition has since October 11 issued near-daily reports of bombing around Marib, saying it has since killed more than 2,500 insurgents.

Marib, capital of the oil-rich province of the same name, is the internationally recognised government's last bastion in northern Yemen.

The Iran-backed Shiite Huthis began a major push to seize the city in February and, after a lull, they renewed their offensive in September.

AFP cannot independently verify the death tolls reported by the coalition, and the Huthis rarely comment on their losses.

Grundberg also offered his condolences after a rebel mortar attack last month on Taez, Yemen's third city, left six children dead or critically injured.

"Again, as elsewhere in Yemen, it is the civilians that bear the burden of this conflict," he said.

The coalition intervened in Yemen in 2015 to shore up the government, a year after the Huthis seized the capital Sanaa.

Tens of thousands of people, mostly civilians, have since been killed and millions displaced in what the United Nations calls the world's worst humanitarian crisis.