PARIS (Reuters) - Atos SE (>> ATOS) said it had agreed to buy Bull SA (>> BULL) on Monday in an all-French IT sector deal worth 620 million euros ($845.2 million) aimed at creating Europe's biggest business in cloud operations and a leading cybersecurity company.

At 4.90 euros a share, the offer represents a 30 percent premium to the three-month weighted average share price of Bull, the companies said, adding that they expected the deal to deliver 80 million euros annually in cost synergies.

Atos said the deal would enhance its offerings in mission-critical solutions for manufacturing, healthcare, and the public sector, and would reinforce its footprint, "mainly in France, but also in geographies such as Iberia, Poland, Africa and Brazil."

"Bull will bring critical and complementary capabilities in big data which, combined with Atos solutions, will create a unique offering in this high-growth segment," the statement said.

Bull's main shareholders, Crescendo Industries and Pothar Investments, own some 24.2 percent of the company and have already committed to tender their shares, the companies said.

Atos is also involved in a battle to acquire French IT services group Steria (>> GROUPE STERIA). Steria has accepted a bid from rival Sopra (>> SOPRA GROUP) and rejected Atos' proposed 22 euro per share proposal.

A spokesman for Atos said the Bull deal did not change anything about its offer for buy Steria, which remains on the table until Sopra's annual meeting on May 27.

(Reporting by Andrew Callus and Gwenaelle Barzic; Editing by Miral Fahmy)

Stocks treated in this article : ATOS, SOPRA GROUP, GROUPE STERIA, BULL