Turkish President Recep Tayyip Erdogan says he doesn't believe that Egypt's former president Mohammed Morsi died of natural causes.

Erdogan made the comments Tuesday at an Istanbul mosque, where hundreds held funeral prayers for Morsi, Egypt's first democratically elected president who was ousted by the military in 2013.

Morsi died Monday after collapsing during a trial session.

Erdogan said: "Mohammed Morsi walked to join God during the trial. Whether this was a normal walk, or were there some other conditions involved, this is something to think about."

He continued: "I don't believe that this was a normal death."

Erdogan also criticized authorities in Egypt for not allowing Morsi to be buried at his family's cemetery in his hometown.

Earlier, the Turkish leader, who had forged close ties to Morsi, criticized Western nations for not speaking out against Egypt's current government.