More than one million civilians have fled Ukraine because of the Russian invasion, according to the United Nations (UN).

The European Union (EU) says up to four million people may try to leave and that it will welcome refugees with "open arms".

Refugees are crossing to neighbouring countries to the west, such as Poland, Romania, Slovakia, Hungary and Moldova. Smaller numbers have gone to Russia and Belarus.

The UN says that so far:

Almost 90,000 people have moved on from these countries to others in Europe.

Many people have waited up to 60 hours to cross into Poland, in freezing weather. Those entering Romania have waited up to 20 hours.

Many have not been able to board trains leaving Ukrainian cities.

Refugees are told they do not need documents, but should preferably have their internal or foreign passports, birth certificates of children travelling with them and medical documentation.

To get refugee status, they need to be Ukrainian citizens or people legally living in Ukraine, such as foreign students.

In Poland and other countries bordering Ukraine, refugees can stay in reception centres if they do not have friends or relatives to stay with. They are given food and medical care.

Poland is also preparing a medical train to transport wounded Ukrainians.

Hungary and Romania are offering cash allowances for food and clothing. Children are being given places in local schools.

The Czech Republic will allow refugees to apply for a special type of visa in order to remain.

Poland and Slovakia have asked the EU for help providing for refugees. As a result, Greece and Germany are sending tents, blankets and masks to Slovakia, while France is sending medicine and other medical equipment to Poland.

The EU is preparing to grant Ukrainians who flee the war a blanket right to stay and work throughout the 27 nations for up to three years.

They would also receive social welfare and access to housing, medical treatment and schooling for children.

Prime Minister Boris Johnson says the UK could take in 200,000 Ukrainian refugees.

Businesses will also be able to sponsor a Ukrainian to come to the country. The Home Office is expected to outline more details shortly.

Ukrainians can apply for a family migration visa if they are an immediate family member of a British national who usually lives in Ukraine.

The Kyiv visa processing centre is currently closed but the office in the western city of Lviv is open, and people can also apply from centres in nearby countries.

The UN estimates says at least 160,000 people in Ukraine who have fled the war are displaced within their own country.

The EU believes that figure could climb to seven million, and that 18 million Ukrainians will be affected by the war.

The UN's High Commission for Refugees says it is trying to help internally displaced people, but the war is making it unsafe for aid workers.

The UN is preparing to deliver assistance in western Ukraine, where access is easier.