(Reuters) - Rizvi Traverse Management LLC, managed by secretive investor Suhail Rizvi, has halved its stake in Twitter Inc and increased its holding in mobile payments company Square Inc, regulatory filings showed on Friday.

When Twitter's IPO was in the works, Suhail Rizvi quietly amassed a stake of more than 15 percent in the microblogging phenomenon for himself and his investors, Reuters reported.

Rizvi also played a role in convincing Kingdom Holding Co, Saudi Prince Alwaleed bin Talal's investment company, to buy additional Twitter stock, Reuters reported in 2013.

His private-equity firm owned 1.4 million Twitter shares as of June 30, down 50 percent from March 31, according to a filing. That would give him a stake of about 0.2 percent, according to a Reuters calculation. (http://bit.ly/2bnAgNl)

The firm's stake in Square rose to 1.05 million Class A shares from about 44,000. That works out to a stake of about 0.3 percent. Both Twitter and Square are run by Jack Dorsey.

Twitter recently reported its slowest quarterly revenue growth since going public in 2013 as it struggles to attract users, while Square posted a big jump in revenue and a smaller loss.

Rizvi, once a dealmaker focused on Hollywood, is known for being super-secretive.

Reuters has reported that he once hired a person to scrub his picture from the internet. (http://reut.rs/2aOA9o6)

Rizvi also owns stakes in Elon Musk-led SpaceX, Snapchat, Playboy and fitness device maker Jawbone and previously held a stake in Facebook Inc.

(Reporting By Sai Sachin Ravikumar and Sudarshan Varadhan in Bengaluru; Editing by Ted Kerr)