Los Angeles: Pop diva and actress Jennifer Lopez reportedly had an awkward reunion with ex-boyfriend Diddy at a post-Oscars party, where she apologised to him for unreturned calls.

The singer-actress, 42, was at Vanity Fair's star-packed after party with her current beau Casper Smart, when she encountered the rapper.

According to an observer, Lopez made a bee-line for her ex, whom she dated from 1999 to 2001, shortly after arriving, as reported.

Although the 'American Idol' judge seemed "friendly" during their chat, she was overheard apologizing for not returning his calls and text. "It was weird," the observer added.

Lopez, who famously dated Ben Affleck after splitting with the hip-hop mogul then known as Puff Daddy (real name Sean Combs), 42, has been friendly with another ex, Marc Anthony.

She and her husband of seven years (they shared twins Emme and Max, 3) announced their split last July but remain colleagues on their reality show 'Q'Viva!'