Heidi Klum splits from beau Martin Kirsten - report

Supermodel-turned-reality TV star Heidi Klum has reportedly split from her bodyguard boyfriend Martin Kirsten after 18 months of dating.

The German beauty is single once again, a close friend confirms to People magazine.

The source tells the publication, "Martin was there for her during a challenging time in her life and it was something she will always be grateful for.

"Life is about timing. He was incredibly supportive and they were there for each other, but they're moving on now. They still have a great friendship."

The former couple has also ended its professional relationship - Kirsten no longer works as Klum's bodyguard.

Klum and Kirsten began dating in the summer of 2012, just months after the model filed for divorce from her estranged husband Seal.

The singer was initially against the romance and when he was asked for a reaction to the news that his ex was dating Kirsten, he stated, "Whilst I didn't expect anything better from him, I would have thought that Heidi would have shown a little more class and at least waited until we separated first before deciding to fornicate with the help."