** Telecom services provider Idea Cellular's shares rise as much as 13 pct to 116.45 rupees

** Idea to demerge tower business portfolio and sell majority stake to American Tower Corp, CNBC tweets, citing unidentified sources (http://bit.ly/2nDbQ3t)

** Idea and ATC seek to close deal before a proposed Idea merger with Vodafone India, CNBC tweets

** Idea Cellular was not immediately available for comment; email queries to ATC were not answered outside of regular business hours

** Idea's shares have risen about 32 pct since Jan. 27, when both Idea and Vodafone confirmed talks of a merger