BENGALURU, Oct 13 (Reuters) - India's Infosys Ltd on Thursday reported a bigger-than-expected increase in second-quarter profit, boosted by strong margin growth, and tightened its full-year revenue growth forecast amid an uncertain global environment.

The country's No.2 IT services company by revenue now expects 15%-16% revenue growth in the fiscal year ending March, compared with the 14%-16% rise it had forecast in July.

"We continue to see good traction (in terms of deal wins)," said Salil Parekh, chief executive officer and managing director of Infosys.

While it signed 27 large deals in the quarter, with the total contract value at a seven-quarter high of $2.7 billion, Infosys trimmed its operating margin guidance for the year to 21%-22% from 21%-23%.

"We also see some caution in hi-tech and telecom besides mortgage and financial services. Keeping both the positive and macro factors we have decided to make our guidance narrower at the higher end of the band we had," said Parekh.

Infosys's rivals had also issued similarly cautious outlooks earlier this week, due to the challenging macro-environment and fears of an economic slowdown in their major markets of the U.S. and Europe.

Larger rival Tata Consultancy Services Ltd had said clients are taking longer to decide on bigger deals, while smaller rival Wipro gave a weak outlook for the current quarter.

Infosys's consolidated net profit rose about 11% to 60.21 billion Indian rupees ($729 million) year-over-year in the quarter ended Sept. 30, beating analysts' estimate of 57.82 billion rupees, according to Refinitiv data.

Its revenue from operations jumped 23.4% to 365.38 billion rupees, while margins rose 140 basis points sequentially to 21.5%.

Infosys also approved a share buyback worth 93 billion rupees. ($1 = 82.5920 Indian rupees) (Reporting by Nallur Sethuraman in Bengaluru and Munsif Vengattil in New Delhi; Editing by Savio D'Souza)