“Congrats to Olivier Martinez and Halle Berry!! #wedding,” the Australian pop star, 43, wrote on Twitter.
Minogue and Martinez dated for four years before splitting in 2007. While they were dating, Minogue credited the French actor for helping her through the dark days of her battle against breast cancer.
“He was incredible,” she said. “He didn’t hesitate in canceling work and putting projects on hold so he could be with me. He’s the most honorable man I have ever met.”
A rep for jewelry designer Gurhan told PEOPLE Wednesday that Martinez gave Berry a diamond-and-emerald engagement ring. But neither party has confirmed the couple plan to marry.