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No bombs were found, but the threats are part of a wave of intimidation against companies that form the backbone of India's growing IT industry.
A smaller Wipro office was targeted as part of a previous hoax and all the scares could be linked to reported plans by separatist terrorists to destabilise Bangalore's software companies.
UK companies outsourcing software development work to India may now have to check that their offshore partners' business continuity plans are up to scratch.
Analyst group Forrester said, "Companies that rely on Indian suppliers to provide them with IT and BPO services should revisit their contingency plans and make sure that their India-based resources are secure in the event of further disruptive behaviour."