* Q1 net loss 99.6 mln riyals, flat y-o-y - statement

* Reduced staffing by 10 pct in May

* Mobile customers up 2.6 pct, revenue down 7 pct

(Adds detail, context)

By David French

DUBAI, July 26 (Reuters) - Vodafone Qatar , an affiliate of Vodafone Group , reported on Tuesday a first-quarter loss that was flat compared with the corresponding period of last year, as higher customer numbers offset a decline in total revenue

The telecoms operator made a net loss of 99.6 million riyals ($27.4 million) in the three months to June 30, it said in a bourse statement, compared with a loss of 99.9 million riyals in the prior-year period.

The result was in line with the forecast of QNB Financial Services, which expected a net loss of 101.2 million riyals.

Vodafone Qatar, whose financial year starts on April 1, has yet to make a quarterly net profit since ending state-controlled Ooredoo's domestic monopoly in 2009.

The flat year-on-year result comes after the firm's losses had widened in the previous six quarters as Ooredoo slashed prices and fought hard to bolster its revenue share.

In the statement, Vodafone Qatar Chief Executive Ian Gray said the operator had reduced headcount by 10 percent in May, with some job cuts permanent and other positions to be reassigned to roles aimed at boosting mobile revenue streams.

It said when announcing its full-year earnings in May it planned to cut its workforce by a tenth, although gave no details at the time.

Its first-quarter earnings were aided by a 2.6 percent increase in mobile customers to 1.458 million. Mobile average revenue per user (ARPU), a key industry indicator, was up 2.1 percent on the fourth quarter of its financial year, although down 9 percent on the same quarter last year.

Vodafone Qatar generated total revenue of 501 million riyals in its first quarter. This was down 7 percent from the prior-year period, the statement said.

Gray added that while international voice revenue continued to decline, revenue from data usage was higher.

($1 = 3.6414 Qatar riyals)

(Editing by Muralikumar Anantharaman and Mark Potter) ((davidj.french@thomsonreuters.com; +971 4 362 5864; Reuters Messaging: davidj.french.thomsonreuters.com@reuters.net))