NEW YORK, May 13 (Xinhua) -- Global index compiler MSCI announced Monday that it is set to double the weight of China A-shares, or Chinese mainland shares denominated in yuan, in its benchmark indexes, which will become effective as of market close on May 28.

The move came as the first step of the weight increase of China A-shares in the MSCI Emerging Markets Indexes.

The overall increase has been planned in three stages, which will ultimately quadruple Chinese stocks' weighting by November, the New York City-based company said on March 1.

This month, 26 China-A shares, 18 of which are ChiNext stocks, will be added to the MSCI China Index, which will uplift the inclusion factor for 238 existing constituents from 5 percent to 10 percent, MSCI said in a Monday statement.

An inclusion factor of 10 percent indicates 10 percent of market capitalization of large cap stocks to be included into the indexes.

As initially planned, the percentage of all large cap China A-shares in the MSCI indexes is scheduled to rise to 15 percent in August in the second stage. The final step will see the number at 20 percent in November.

Meanwhile, MSCI will also add mid cap China A-shares, including eligible ChiNext shares, with a 20 percent inclusion factor to the MSCI indexes.

The first-step increase will make China A-shares account for an aggregate weight of 5.25 percent and 1.76 percent in the MSCI China Index and MSCI Emerging Markets Index, respectively, MSCI said.