JERUSALEM, Dec 21 (Reuters) - Mizrahi-Tefahot (MZTF.TA), Israel"s third-largest bank, said on Tuesday it raised 1.8 billion shekels ($569 million) in a debt offering that expanded two existing bond series. Demand from institutional investors reached some 3 billion shekels, Mizrahi said. One series of 5.6 year bonds raised 1.2 billion shekels and will pay interest of 0.78% above comparable Israel government bonds. A second series of 8.5 year bonds raised 600 million shekels at 0.82% above government bonds. So far in 2021, the bank has raised nearly 5.5 billion shekels in debt plus $600 million in an international bond offering. ($1 = 3.1631 shekels)