As Europe grapples with its biggest migrant crisis in recent history, Hollywood celebrities are rallying to raise awareness about the issue and lashing out at calls to turn away refugees.

Oscar-winning actress Susan Sarandon this month became the latest star to arrive on the Greek island of Lesbos, a frontline for the crisis, where she is spending the Christmas holiday helping new arrivals and writing about her experience for the Huffington Post and RYOT.org, a virtual reality news company.

The 69-year-old actress, who is known for her support of humanitarian causes and is a goodwill ambassador for the UN Children's Fund (UNICEF), said she was trying to raise awareness on the crisis to honor her grandparents, who were Italian immigrants.

"I hope that I can make it possible for them (the refugees) to have a voice so we can understand," she wrote in one posting. "Understand that 'these people' are just like us, wanting to keep their children safe. Wanting them to have a future."

The support by Sarandon and other celebrities comes against a backdrop of inflammatory remarks in the United States, where leading Republican presidential candidates and politicians have backed calls to prevent Muslims or Syrian refugees from entering the country.

Republican presidential frontrunner Donald Trump has also called for registering all Muslims in the US while his rival Ben Carson has said allowing Syrian refugees into the country was tantamount to exposing a neighborhood to a "rabid dog."

Actor Mandy Patinkin, who plays CIA operative Saul Berenson on the hit television series "Homeland" and who visited Lesbos earlier this month, said such rhetoric only served to fan the flames of intolerance.

"This fear-mongering and hatred that's going on by people running for the president of United States is so misguided," he said during an appearance on the popular "Late Show" with Stephen Colbert. 

"It is important that we open up our arms and our hearts to refugees that are fleeing a horrifying situation."

 'Need to reach out'

Actor Edward Norton has also spoken out on the migrant crisis and has raised nearly $460,000 on behalf of a Syrian refugee whose story prompted him to act.

The Syrian, a scientist who lost seven members of his family in a bombing two years ago -- including his wife and a daughter -- was featured on the website "Humans of New York" earlier this month. 

The man has been living in Turkey for the past two years but is expected to move to the US state of Michigan.

"I saw this story on one of my favorite sites, Humans of New York, and it moved me to tears," said Norton, who has starred in films including "The Incredible Hulk," "Fight Club" and Oscar-winning dark comedy "Birdman."

"Let's reject the 'anti-human' voices that tell us to fear refugees and show this man and his family what Americans are really made of," he added.

British actor David Morrissey, best known for his role in the popular zombie series "The Walking Dead," said it was essential for the world to act on the crisis.

"We can't turn a blind eye to this," said Morrissey following his trip this summer to Lesbos with the UN refugee agency (UNHCR). "We need to reach out, to help, as we would want people to reach out and help us."

Across Europe, A-listers are similarly rallying to the migrant cause.

In October, Oscar-nominated British actor Benedict Cumberbatch grabbed headlines after telling a theater audience in London "f--k the politicians"
before making a despairing plea on behalf of the thousands of refugees arriving daily in Europe.

According to the UNHCR, more than one million migrants and refugees reached Europe this year, including 970,000 who made the dangerous journey across the Mediterranean.

US President Barack Obama has pledged to take in 10,000 Syrian refugees over the course of the next year, five times the number the US has taken in since 2012. (AFP)