A Dutch train driver held in captivity for more than three years by Islamic militants has expressed his gratitude to the French troops who liberated him this week in northern Mali.

In a written statement released Thursday by the Dutch foreign ministry, Sjaak Rijke says he is in good health after working out using improvised equipment during his captivity but adds that his captivity was mentally draining.

He says, "I don't know how much longer I could have endured it. So I want to express my huge gratitude to the French elite troops who freed me."

Rijke, who was abducted from a hotel in northern Mali in November 2011, says his rescue early Monday "was a very hectic and scary moment, but I'm alive and I'm free!"