Nicholas Winton, a Briton who saved hundreds of Jewish children in Prague from the Nazis in the run-up to World War II, has died at the age of 106, his family said on Wednesday.

Son-in-law Stephen Watson said Winton died peacefully in his sleep at Wexham Hospital in Slough, west of London.

Born in London of German-Jewish parents, Winton travelled to Nazi-occupied Czechoslovakia -- which split into the Czech Republic and Slovakia in 1993 -- as a young employee of the London Stock Exchange.

It was there that he organised trains that transported some 669 children, most of them Jews, to Britain in 1939, saving them from concentration camps and near-certain death.

An additional train was set to leave on September 3, 1939, the day Britain declared war on Germany, but the borders were already sealed. None of the 250 children were seen again.

Winton's efforts earned him the nickname "English Schindler" in reference to Oskar Schindler, the German industrialist who rescued hundreds of Polish Jews during the war.

"A good man, Sir Nicholas Winton, has passed away. He will remain forever a symbol of courage, deep humanity and incredible modesty," Czech Prime Minister Bohuslav Sobotka said on Twitter.

President Milos Zeman tweeted: "He was a man I admired for his courage."

British Prime Minister David Cameron tweeted: "The world has lost a great man. We must never forget Sir Nicholas Winton's humanity in saving so many children from the Holocaust."

Winton kept quiet about his mission for 50 years until his wife found evidence of it in their attic.

He was knighted in 2003, and his Czech supporters have repeatedly petitioned for him to receive the Nobel Peace Prize.

"He was incredibly unique in that he didn't tell anyone for such a long time" about his wartime activities, said Tomas Kraus, head of the Czech Federation of Jewish Communities.

"He wasn't the only one, there were more such personalities. In his case, it's the modesty that's so unique, he considered it an unimportant episode in his life."