LONDON (Reuters) - Cut-throat competition in India and an onslaught from rivals in its home market prompted Britain's Vodafone (>> Vodafone Group plc) to nudge its full-year earnings guidance down on Thursday sending its share price lower.

Competition in India has been ramped up by free offers from new entrant Reliance Jio Infocomm (>> Reliance Industries Limited), but Vodafone plans to fight back by merging its Indian subsidiary with smaller rival Idea Cellular (>> Idea Cellular Ltd).

"This is about creating an amazing asset and a very strong company, not about retrenching," Vodafone Chief Executive Vittorio Colao said.

Vodafone, the world's second-biggest mobile phone group, has built its name through rapid global expansion in a series of bold deals in the 1990s and 2000s and is the second-largest player in India.

Overall, service revenue in Europe grew by 0.7 percent in its third quarter, down from 1 percent in the second quarter. In its emerging markets -- including India, Africa and Turkey -- growth slowed to 3.9 percent from 7.1 percent.

Shares in the company fell as much as 3 percent on Thursday morning. By 0934 GMT they were down 1.3 percent at 190 pence

Britain remained tough, with service revenue declining by 3.2 percent, which it said reflected increased competition in the business sector, an area of strength for the operator.

Finance Director Nick Read said the company was seeing competition in corporate business from EE, now owned by BT (>> BT Group plc), and from O2, owned by Telefonica (>> Telefonica SA).

"Everyone is chasing growth and customers," he said.

Vodafone reported a 1.7 percent rise in overall organic service revenue for the quarter, broadly in line with analyst expectations.

The company reiterated its target to generate at least 4 billion euros of free cash flow in the year to March 31, but it said it now expects core earnings to come in at the lower end of a range of 3-6 percent growth.

"These results are not surprising given the evidence of the deterioration in India but have few specific positives either," Citi analysts said.

"The effective cut to EBITDA guidance looks realistic but will raise questions about full-year 2018 trajectory."

(Editing by Kate Holton and David Goodman)

By Paul Sandle