SHANGHAI (Reuters) - China's main stock indexes were flat on Monday, bucking the upward trend in Asian markets, as sentiment was subdued amid concerns of yuan depreciation and a fresh regulatory crackdown on speculative trading.

Both the blue-chip CSI300 index <.CSI300> and the Shanghai Composite Index <.SSEC> rose just 0.1 percent, to 3,112.67 points and 2,888.59 points, respectively.

On Monday, other Asian markets had solid gains on hopes Britain will decide to remain in the European Union.

Last week, U.S. publisher MSCI decided not to add yuan-denominated Chinese shares to its emerging market index. Many watchers say the decision at least partly reflected fund managers' unease about allocating more to yuan assets.

Responding to yuan depreciation fears, the Financial News, a paper owned by China's central bank, said in a commentary on Monday that although there is no concrete basis for depreciating the yuan over the long term, more two-way volatility is unavoidable while reforms proceed.

Market sentiment was also hit by a weekend announcement from China's securities regulator that it would tighten rules on major restructurings by listed companies to curb speculation around shell companies used for backdoor listings.

Sector performance was mixed. Real estate shares strengthened after data showed China's home prices rose faster in May as smaller cities joined the rally in bigger cities.

(Reporting by the Shanghai Newsroom; Editing by Richard Borsuk)