A blaze tore through a refugees camp on the Greek island of Lesbos overnight, leaving roughly 12,000 people without shelter on Wednesday.

No casualties have yet been reported but among those displaced at the Moria camp are 4,000 children, according to the United Nations' refugee agency UNHCR.

"We're talking also about people who are vulnerable people, who have fled their country, so they already have physical or psychological traumas," Stella Nanou, spokesperson for UNHCR in Greece, told NBC News. "They need to be assisted as soon as possible."

The cause of the fire, which has left the camp largely destroyed, is not yet known.

Aid organizations are now scrambling to find temporary shelter for the refugees and asylum seekers to support them in the coming day, Nanou said.

Greek Prime Minister Kyriakos Mitsotakis was also convening an emergency ministerial meeting Wednesday morning to examine the situation and decide on measures to be taken, his office said.

For months, UNHCR and other aid groups have been calling on improvements for what has been described as an "alarming" situation at the camp, Nanou said.

The camp — designed to host just 3,000 refugees — was four times overcapacity.

Refugees have been flooding the Greece's islands since the 2015 crisis, leaving Moria camp to host 20,000 refugees and asylum seekers at its peak. People at the camp were largely from Afghanistan, Syria, Iraq and Palestine, Nanou said.

While numbers have since declined, conditions remained overcrowded, unsanitary and unsafe when the fire sparked, Nanou said. More than half the population were living in makeshift shelters or summer tents.

At least 400 unaccompanied children are among the group, as well as pregnant women and elderly people. One building had been identified as a possible shelter for those children Wednesday, Nanou said, while more tents and materials that can be used as makeshift tents are being collected.

Tensions are also running high between the refugees and residents of nearby towns, she said, raising concerns this could cause conflicts as people are pushed from the camps into the wider community.

"Our call to everyone is to exercise restraint," she said.

Aid groups are also concerned about the spread of the coronavirus among refugees. At least 35 people have tested positive for the virus, Nanou said, and were under quarantine.

"Those who were living in Moria are now left with nothing; already traumatized people have now lost what few belongings they had," Dimitra Kalogeropoulou, Greece country director for the International Rescue Committee said in a statement.

Kalogeropoulou said support from the international community was needed to find a long term solution.

"It is high time that EU countries work with the Greek government to urgently relocate refugees and asylum-seekers not only to the Greek mainland but also to other EU countries," she said.

European Commission Vice President Margaritis Schinas, who is responsible for migration matters, tweeted that he had been in touch with Greece's Prime Minister and “assured him that the European Commission is ready to assist Greece immediately at all levels at this difficult time.”

While tragic, Nanou said the crisis may now force everyone to take much-needed action on the living conditions of the refugees.

"Perhaps now, you know, there is an opportunity out of this disaster to identify some solutions for these people," she said./NBC