President Alar Karis said that Siim Kallas was an important statesman.
He said that Siim Kallas helped Estonia become stronger and more European.
Karis wrote that Siim Kallas was a brave and active man.
He said that Siim Kallas helped Estonia join the European Union and NATO.
The President expressed condolences to Siim Kallas's family and friends.
Former presidents Toomas Hendrik Ilves and Kersti Kaljulaid also wrote about Siim Kallas.
Ilves said that Siim Kallas was a great thinker and doer.
He said that Siim Kallas was his role model.
Kaljulaid recalled their cooperation during the currency reform.
She said that they often discussed the future of the European Union.
Kaljulaid said that Siim Kallas made many bold decisions.
She thanked Siim Kallas for everything he did.
Siim Kallas passed away on Saturday.