Geneva ( AP) - The United Nations refugee agency said on Wednesday that more than 4 million refugees have now fled Ukraine since Russia launched its war, marking the largest refugee crisis in Europe since World War II.

The new figure was posted on the UNHCR website. More than 2.3 million people have arrived in Poland, but many have traveled to other countries or returned to Ukraine.

Relief workers say numbers have declined in recent days as many people await developments in the war. About 6.5 million people have also been displaced within the country.

More than 608,000 people have entered Romania, over 387,000 have gone to Moldova, and about 364,000 have entered Hungary since the war began on February 24, based on figures provided by governments.

Since the start of the war, the agency had expected around 4 million people might flee Ukraine - although it has repeatedly said it is revising its estimates.

Meanwhile, the UN High Commissioner for Refugees Filippo Grandi wrote on Twitter while crossing the border into Ukraine: "The number of refugees from Ukraine now totals 4 million, after five weeks of the Russian invasion."

Grandi said he would be present in the western city of Lviv and discuss ways to increase its support "for those affected and displaced by the war ".

Meanwhile, the agency's teams and partners are working to provide protection and emergency shelter as well as cash assistance, essential relief items, and other vital services for those who have fled.

Editing: Dima Abu Khair