Preparing to step up relief efforts in Ethiopia's Tigray region, United Nations (UN) humanitarian staffers on Tuesday said a breakdown in communications following a ceasefire announcement leaves the situation fluid and unclear.

"The consequences and impact of the declaration of an immediate ceasefire remain unclear," said Stephane Dujarric, the chief spokesman for UN Secretary-General Antonio Guterres.

"Our humanitarian colleagues tell us there has been a breakdown of telecommunications and internet services in Tigray as of today (Tuesday)," said Dujarric, adding that "the impact of the current situation on the humanitarian operations remain unknown at this moment."

The latest reports were that all UN humanitarian staffers in the regional capital of Mekelle and the town of Shire are safe and sound, but "the situation remains rather fluid at this point."

There were no staff evacuations, said Dujarric. But the world organization moved some staff temporarily to a hotel in Mekelle.

A unilateral ceasefire was declared in the northernmost Tigray region by the Ethiopian government late Monday.

The conflict hampered humanitarian operations before the stand-down, the spokesman said. Entire operations will resume, pending security and access assessment of the new situation.

Access denial plagued the humanitarian operation in Tigray since the conflict started in early November.

"We are staying and delivering for the people of Tigray, but we will need access to vital supplies that are currently not available," he said, adding that "staffing levels at the moment remain the same, as the airport in Mekelle is closed and routes are not open."

The ceasefire "will obviously, we hope, help improve humanitarian access and the assistance we are able to deliver," he said.

"It is very important for steps to be taken for unity through political dialogue and of course we continue to offer the full support of the United Nations in this regard," he said.