Recasts after market opening, adds share price details

May 13 (Reuters) - Indonesia's benchmark stock index .JKSE slid to a one-year low and shares of some companies owned by the nation's richest families tumbled, after MSCI MSCI.N removed six firms from its Indonesia global standard index.

The index provider announced on Tuesday it had removed Amman Mineral International AMMN.JK, Chandra Asri Pacific TPIA.JK, Dian Swastatika Sentosa DSSA.JK, Barito Renewables Energy BREN.JK, Petrindo Jaya Kreasi CUAN.JK and Sumber Alfaria Trijaya AMRT.JK from the MSCI Indonesia Index following a quarterly review.

That sent the Jakarta Composite ‌Index sliding 1.7% to a one-year low shortly after the open on Wednesday, with shares of most of the affected companies tumbling more than 10%.

The exception was Sumber Alfaria Trijaya, whose shares last traded 4% lower, as the company was moved to the MSCI Indonesia small cap index.

The revision following MSCI's comments last month that it will extend its review of ‌Indonesia's stock market to June to assess reforms announced by the Southeast Asian nation, after a warning in January triggered a market rout and a foreign investor exodus.

The move could drive forced selling from passive index-tracking funds once the rebalancing comes into effect on May 29.

The index provider had at the start of the year warned that Indonesia could be downgraded to "frontier" market status from "emerging", citing concerns over highly concentrated company ownership structures and transparency problems.

Indonesian business magnate Prajogo Pangestu has controlling stakes in Chandra Asri, Barito Renewables and Petrindo Jaya Kreasi.

Dian Swastatika Sentosa is part of the Sinar Mas Group, one of the country's largest conglomerates owned by the billionaire Widjaja family.

In Tuesday's move, MSCI also removed 13 Indonesian companies from its small cap index list, including state miner Aneka Tambang ANTM.JK and several palm oil companies such as conglomerate Astra Group's Astra Agro Lestari AALI.JK and Sinar Mas Group's real estate firm Bumi Serpong Damai BSDE.JK.

MSCI said in April it would continue to freeze increases ​to foreign inclusion factors and the number of shares for Indonesian securities. It will also refrain from adding Indonesian stocks to its investable market indexes or allowing any upward migration across size segments.