* Ozon, Russia's Amazon, increases IPO amount - sources

* Plans to use proceeds to fund expansion - sources

* Company seen valued at $4-$12 billion - sources

* Baring Vostok controls around 40% in Ozon

MOSCOW, Nov 13 (Reuters) - Russian online retailer Ozon plans to raise about $750 million in an initial public offering (IPO) in the United States to help fund its expansion in a rapidly-growing e-commerce market at home, three financial market sources said.

Russia's fragmented e-commerce market is forecast to grow by more than 40% to 2.5 trillion roubles ($32.4 billion) this year, according to Euromonitor research group, and by 10-15% a year over the next five years.

Revenues at Ozon, a Russian version of U.S. e-commerce giant Amazon.com Inc, surged as much as 70% in the first nine months of the year, as people switched to online shopping in the coronavirus pandemic.

Ozon was initially aiming for $500 million in the IPO, but has since raised that to $750 million, the sources said.

Ozon declined to comment.

Russian conglomerate Sistema and private equity firm Baring Vostok control nearly 40% each of Ozon.

Separately, a Russian court ruled on Thursday that U.S. investor Michael Calvey and other Baring Vostok executives may be released from house arrest in an embezzlement case linked to mid-sized Russian bank Vostochny.

The sources said Ozon planned to use proceeds from the IPO to fund its expansion and that the final size of the share offering was yet to be determined.

One of the sources said an official announcement on the price range was expected next week, if the IPO is approved by the U.S. Securities and Exchange Commission.

If that timeline is not met, the IPO might not happen this year, the source added. However, a second source said the IPO could still happen after the Thanksgiving holiday in the United States later this month.

One of the sources said Sberbank CIB, one of the IPO's organisers, had valued the company at $4-$8.5 billion.

Another organiser, VTB Capital, has valued it at $4.7-$7.1 billion, a second source said, while Goldman Sachs, also working on the IPO, has valued it at $6-$12 billion, a third source said.

($1 = 77.2400 roubles) (Reporting by Olga Popova Additional reporting by Anna Rzhevkina and Alexander Marrow writing by Gabrielle Tétrault-Farber and Katya Golubkova Editing by David Goodman and Mark Potter)