(CNN) — Actors Blake Lively and Ryan Reynolds are promising to match every donation up to $1 million for refugees fleeing war in Ukraine, the couple said on social media.

“In 48 hours, countless Ukrainians were forced to flee their homes to neighboring countries. They need protection. When you donate, we’ll match it up to $1,000,000, creating double the support,” Reynolds wrote Saturday on Twitter in promoting donations to the United Nations refugee agency.

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Lively posted a UNHCR photo on Instagram showing a child, saying the agency is “providing life saving aid.”

Ukrainians crowded onto trains and waited in long lines for hours to leave the country after Russia invaded neighboring Ukraine on Thursday. About 368,000 refugees have managed to leave, the United Nations High Commissioner for Refugees reported Sunday.

EU Commissioner for Home Affairs Ylva Johansson said Sunday the European Union needs to prepare for millions of refugees to arrive.

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“It’s very difficult to guess how many, but I think we should be prepared for millions,” Johansson said.

The UN agency said that because of “years of violence,” more than 2 million people had left Ukraine even before Russia troops invaded last week, and almost 3 million people in Ukraine will need humanitarian assistance this year.

“Those fleeing for their lives need immediate shelter, protection and safety,” the non-profit USA for UNHCR said on the site where donations can be made.

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