The number of Ukrainians fleeing abroad is now 4,019,287, the United Nations' Refugee Agency (UNHCR) said on Wednesday.
The new figure was posted on an UNHCR website. More than 2.3 million have arrived in Poland, but many have traveled onward to other countries or back into Ukraine.
Aid workers say the numbers have eased in recent days as many people await developments in the war. An estimated 6.5 million people have also been displaced from their homes within the country.
Ukrainian officials reported shelling around the capital Kyiv and the northern region of Chernihiv on Wednesday, despite a promise by Moscow to scale down military operations there.
Russian forces were also shelling nearly all cities along the front line separating Ukrainian government-controlled territory from areas held by Russian-backed separatists in the eastern Donetsk region, the regional governor said, and heavy fighting was reported in the southern port city of Mariupol.
Oleksiy Arestovych, an adviser to President Volodymyr Zelenskiy, said Russia was transferring forces from northern Ukraine to eastern areas to try to encircle Ukrainian troops there.
He said Russia would keep some troops near Kyiv to try to prevent Ukrainian forces reinforcing the eastern front.