������

The UN envoy for Yemen expressed concerns on Wednesday about in the war-wrecked country, urging the warring sides to in six years.

said that while the truce has led to a “significant reduction of violence” in Yemen, there were reports of “some hostile military activities,” particularly around the central

He did not say which side was to blame for the violations but Yemen’s internationally recognized government has accused the of attacking their positions in southern and western Marib. A Houthi spokesman was not immediately available for comment.

“This truce is a step, an important one, but a fragile step, nonetheless," he said. “We need to make the best possible use of the window this truce gives us to work towards ending the conflict.”

Good meeting with Hans Grundberg, our new Special Envoy for . We share a strong commitment to fully support a negotiated, inclusive political settlement to end the conflict in Yemen, a country witnessing the worst humanitarian crisis in the world.

— Rosemary A. DiCarlo (@DicarloRosemary)

The Houthi rebels have been trying for over a year to capture energy-rich Marib from government forces.

But their efforts were dashed in recent months amid increasing support for the pro-government side from the Saudi-led coalition.

Grundberg told a virtual news conference that the was working on a coordination mechanism with the warring sides to maintain the truce, which was announced earlier this month. It is supposed to last for two months.

Grundberg cautioned that the ceasefire is not being monitored by the UN and that the “responsibility to uphold the truce is squarely with the parties themselves.”

Yemen’s brutal civil war erupted in 2014, when the Iranian-backed Houthis seized the capital of Sanaa and forced the government into exile. The Saudi-led coalition entered the war in early 2015 to try restore the government to power.

The conflict has in recent years become a regional proxy war that has killed more than 150,000 people, including over 14.500 civilians. It has also created

The UN-announced truce also includes allowing shipments of fuel to arrive in Yemen’s key port city of and for passenger flights to resume from the airport in Sanaa. Both Hodeida and Sanaa are held by the Houthis.

The UN envoy said he has invited with both sides to convene a meeting to agree on a reopening of roads around Taiz and other provinces as part of the truce.

“We look forward to their responses,” he said.

Taiz, which remains partially held by the forces fighting on behalf of the government, has been blockaded by the Houthis for years.