The United Nations considers humanitarian corridors to be one of several possible forms of a temporary pause of armed conflict.
They are demilitarized zones, in a specific area and for a specific time – and both sides of an armed conflict agree to them.
What are they for?
Via these corridors, either food and medical aid can be brought to areas of conflict, or civilians can be evacuated.
The corridors are necessary when cities are under siege and the population is cut off from basic food supplies, electricity and water.
In cases where a humanitarian catastrophe unfolds because the international law of war is being violated – for example through large-scale bombing of civilian targets – humanitarian corridors can provide crucial relief.
Who sets them up?
In most cases, humanitarian corridors are negotiated by the United Nations. Sometimes they're also set up on the of local groups. Since the corridors need all sides to agree, there is a risk of military-political abuse. For example, the corridors can be used to smuggle weapons and fuel into besieged cities. On the other hand, they can be used by UN observers, NGOs and journalists to gain access to contested areas where war crimes are being committed.
What corridors are established in Ukraine?
In eastern Ukraine, a five-hour ceasefire was to be in place on Saturday, March 5, to allow around 200,000 people from Mariupol and 15,000 residents from the city of Volnovakha to leave.
But the initiative failed after a few hours. The Mariupol city administration said the evacuation had been "postponed for security reasons" because Russian troops continued to bomb the city and its surroundings.
According to news agency Reuters, Russia however said the corridors set up near Mariupol and Wolnowacha had not been used. Russian news agency RIA said, "nationalists" prevented the civilians from escaping and that Russian troops also came under fire during the ceasefire.
Ukraine also said that in the port city of Kherson, Russia had not fulfilled the promise of a corridor and that 19 vehicles with humanitarian aid were not allowed through.
Instead, the Russians themselves planned to send high-profile support to the civilian population, Kherson Mayor Igor Kolykhaiev wrote in a Facebook post: "First they brought the situation to a critical state, and then they rescue us so that we can thank our 'benefactor' for the cameras."
Who gets access?
Access to humanitarian corridors is determined by the parties to the conflict. It is usually limited to neutral actors, the UN or aid organizations such as the Red Cross. They also determine the length of time, the area and which means of transport - trucks, buses or planes – are allowed to use the corridor.
In rare cases, humanitarian corridors are only organized by one of the parties to the conflict. This happened with the American airlift after the Berlin blockade by the Soviet Union in 1948-1949.
Where have they been used?
Humanitarian corridors have been used since the mid-20th century. For example, during the so-called Kindertransport from 1938 to 1939, Jewish children were evacuated to Great Britain from areas under Nazi control.
Humanitarian corridors were also created during the 1992-1995 siege of Bosnian Sarajevo and the 2018 evacuation of Ghouta in Syria.
However, there are many wars and conflicts where calls for civilian corridors or a pause in fighting are in vain. In the ongoing war in Yemen for instance, the UN has so far failed in its negotiations.
