Aug 12 (Reuters) - India's markets regulator has not observed any manipulation in the newly introduced closing ‌auction session that determines closing price levels, the ‌Securities and Exchange Board of India chairman said on Wednesday. The closing auction ​is a big market structure reform in line with global standards, Tuhin Kanta Pandey said at an event in Mumbai. "We are considering all inputs to increase participation," Pandey ‌said, adding that ⁠any new system requires time to settle and attract more participation. The closing auction is a ⁠separate 20-minute session introduced last week in which exchanges collect buy and sell orders to determine a stock's closing ​price at ​a level where the ​maximum volume can be ‌executed. Mutual funds' participation in the new system ‌has risen from around 5%-6% ​on the ​first day to about 20%-25% since then, the regulator said.