The UFC has released two of its most popular heavyweight fighters. Alistair Overeem and Junior dos Santos were recently informed by the promotion that they were being released, sources confirmed with ESPN on Wednesday night.

Dos Santos posted about his release on his Instagram account earlier Wednesday, while MMA Junkie first reported Overeem's release.

UFC officials subsequently confirmed the releases with ESPN's Brett Okamoto.

Overeem had two fights left on his contract, and dos Santos had five left, sources said.

Overeem, a former UFC heavyweight title challenger, previously won the Strikeforce and DREAM heavyweight titles, as well as the K-1 kickboxing World Grand Prix. He suffered a knockout loss to Alexander Volkov in February in his most recent bout. The loss snapped a two-fight winning streak.

Dos Santos, a former UFC heavyweight champion, lost his fourth straight fight in December when he was defeated via TKO by Ciryl Gane.

According to sources close to dos Santos, he was recently offered a short-notice fight against Marcin Tybura at UFC 260 on March 29. After dos Santos declined the fight because of not having enough time to prepare, the promotion ultimately decided to release him, sources said.

In his Instagram post, dos Santos, 37, hinted that he would continue to fight. Overeem, 40, has yet to comment on his future.