Amanda Seyfried's new boyfriend is Veronica Mars actor Justin Long, according to several sources cited by Us Weekly.

The pair has remained low-key about their relationship but an eyewitness at a July 30 event for the Lovelace premiere told the publication that they were "inseparable."

"Justin came alone and stayed close to Amanda all night," the source said. "They weren't making out or anything like that, but they were just inseparable during the event. He hung out when she talked with others."

Speaking about how the Hollywood stars began their romance, another insider said "they've known each other for awhile" and first met when they were each dating other people. Seyfriend's past boyfriends include Dexter actor Desmond Harrington and her Mama Mia co-star Dominic Cooper, while Long was most recently linked to House of Cards star Kate Mara and dated his Going the Distance co-star Drew Barrymore on and off from 2007 to 2010.

"They recently started hanging out more, going on date-like activities. They're both busy ... but they're seeing where it goes," a source said of Seyfried and Long, while another insider said they have a "similar sense of humor."

The A Case of You actor, 35, even showed Seyfried, 27, some affection on Twitter Aug. 10, writing, "Adjectives don't do justice to Amanda Seyfried's fearless + transformative perf in Lovelace."

The stars have yet to publicly comment on their new relationship and Seyfried was recently quoted by TIME magazine saying, "I'm single. I'm just happy being alone and having a dog. Instead of a f***ing suitor.''

Seyfried got her first big break starring opposite Lindsay Lohan in Mean Girls. Long also starred alongside Lohan - in 2005's Herbie Fully Loaded - but got him name on the map following his performance beside Ben Stiller in 2004's Dodgeball: A True Underdog Story and later his lead role in 2006's Accepted.

Tags: Amanda Seyfried Justin Long