STOCKHOLM, Aug 2 (Reuters) - Sweden's Hexagon said on Wednesday that it will recruit more independent board members and further distance its business from Greenbridge, a private investment company controlled by key insiders at the industrial technology group.

The steps follow criticism from short seller Viceroy Research which said on July 19 that Greenbridge and its owners benefited unfairly by front-running Hexagon's investments, a claim both companies have rejected.

Viceroy has focused on an investment in manufacturing company Divergent, claiming that Greenbridge was able to secure a stake ahead of Hexagon. Greenbridge said its stake was in fact bought months later.

Hexagon board Chair Ola Rollen owns 19% of Greenbridge, as does billionaire Hexagon shareholder Melker Schorling's holding company, while three executives of the listed group also hold smaller Greenbridge stakes, according to Hexagon.

"We believe that Hexagon secured maximum value in its investment in Divergent," Hexagon said in a detailed 16-page reply on Wednesday to Viceroy's claims.

But to remove "any future doubt" about the independence of Greenbridge and Hexagon, the two companies have now signed an agreement to keep future investments separate, Hexagon said.

In Wednesday's statement, it quoted an agreement saying: "Greenbridge hereby undertakes in relation to Hexagon not to hereinafter invest in any company, business, or asset where Hexagon, already prior to such investment, has an ownership or other financial or economic interest."

Viceroy said in a response issued to Reuters by Fraser Perring, one of its founders, that it considered Hexagon's statement on Wednesday to be an admission that the company and Greenbridge were considered related parties.

Viceroy, a U.S-based activist short seller, which has in the past targeted other Swedish companies such as SBB and Truecaller, has also criticised Hexagon's accounting and acquisition history as well as its corporate governance.

Hexagon said on Wednesday that Viceroy's claims were full of "demonstrable factual inaccuracies, incorrect assumptions, and unfounded speculation".

In a separate statement, Hexagon said on Wednesday that CEO Paolo Guglielmini had bought one million shares from top shareholder Schorling for 101 million Swedish crowns ($9.5 million).

Hexagon's shares were up more than 2% at 1107 GMT.

Kepler Cheuvreux analyst Johan Eliason said the share price rise was due to the CEO's investment and Hexagon's statement regarding the claims made by Viceroy.

"What I think is good is that they've taken actions to minimise risk going forward," the analyst said. ($1 = 10.6465 Swedish crowns) (Reporting by Marie Mannes and Nell Mackenzie; Additional reporting by Agata Rybska; Editing by Terje Solsvik and Alexander Smith)