Vodafone's turnaround plan kicks off strongly with impressive top-line growth

She said on Monday that organic service revenue had improved "across almost all of our markets", as it reported a 3.7 percent first-quarter rise. "We’ve taken the first steps but of course we have much more still to do," she told reporters.

Shares in Vodafone, which have fallen 43 percent in the last 12 months, rose 4.7 percent in early deals.

The decline in service revenue in Germany more than halved quarter-on-quarter to 1.3 percent, as price rises partially offset the impact of customer losses over the last 18 months.

Della Valle said she expected "ongoing gradual improvement" in the country.

Growth in service revenue in Britain, where Vodafone announced the merger of its operation with Hutchison’s rival network Three last month, accelerated to 5.7 percent, boosted by strong growth in consumer and price increases.

In Italy, improved demand from businesses helped reduce the service revenue decline to 1.6 percent, from 2.7 percent in the previous quarter, it said, while Spain saw a smaller improvement to a decline of 3.0 percent from 3.7 percent.

Della Valle said a strategic review of Spain initiated in May was already driving better performance, but the market needed structural change. "We are considering a range of options," she said.

Vodafone UK Chief Executive Ahmed Essam, who will lead the combined operator, said the company was having early discussions with the antitrust regulator before filing the case in the next few weeks.