Thousands of Americans turned out on Wednesday to feast on fried chicken in a politically charged show of support for a family-owned fast-food chain which opposes same-sex marriage.

Long lines and traffic jams were reported throughout the American heartland after 630,000 people declared on Facebook they would take part in a Chick-fil-A Appreciation Day.

"I just got my chicken and my car is filled with the smell of freedom," a caller named Steve told conservative talk show host Mike Huckabee from the Chick-fil-A outlet at Fort Walton Beach in the Florida panhandle.

"Cars are just everywhere," reported another caller from Florida, named Vicky. "Everybody is coming for Chick-fil-A, freedom and Christianity. It's a beautiful thing."

With more than 1,600 outlets, mainly in the southern United States, family-owned Chick-fil-A is as famous for its Bible Belt values - it never opens on Sunday - as it is for chicken breast sandwiches and nuggets.

But it is under fire from gay rights activists and their supporters who, citing tax records, say it has given millions of dollars to Christian groups that vigorously campaign against marriage equality.

"Guilty as charged," President Dan Cathy told a Baptist publication in mid-July, adding in a subsequent radio interview that the United States is "inviting God's judgment" by recognizing same-sex vows.

His remarks came as the US Supreme Court reflects on whether to rule on the constitutionality of same-sex marriage - now legal in six states, but not at the federal level - when it returns from summer recess.

Critics of Chick-fil-A - who plan a National Same-Sex Kiss Day outside the chain's restaurants and shopping-mall locations on Friday - claim they are getting their message across.

Indeed, global polling institute YouGov said Chick-fil-A's previously high brand perception among consumers has slipped below the national average for all fast-food chains since Cathy made his remarks.

"In an era when corporations are supporting equality at unprecedented levels, Chick-fil-A is on the decidedly wrong side of history," said Fred Sainz of the Human Rights Campaign, a gay and lesbian civil rights group.

US President Barack Obama favors marriage equality, while his Republican rival Mitt Romney insists marriage can only occur between a man and a woman. Both have yet to comment on the Chick-fil-A flap.

Huckabee, a one-time Republican presidential hopeful who harnessed social media to spearhead Wednesday's show of chicken solidarity, told his listeners Cathy was the victim of bullying from the same-sex marriage lobby.

If there is to be diversity in the US, he said, "let's include Christians in that. Let's include people who believe in old-fashioned biblical values. Those folks are Americans, too."

Agence France-Presse