UPDATE 1-Energy boosts euro zone factory prices in May

(Updates with analysts quotes)

By Marcin Grajewski

BRUSSELS, July 2 (Reuters) - Soaring energy costs pushed euro zone producer prices up in May more than expected, data showed on Wednesday, reinforcing speculation the European Central Bank may rise interest rates more than once this year.

Prices at factory gates in the 15 countries using the euro rose 1.2 percent month-on-month for a 7.1 percent annual gain, European Union statistics office Eurostat said.

Economists polled by Reuters had expected a 0.9 percent monthly increase and a 6.7 percent yearly rise.

Eurostat also revised up by 0.1 percentage point the April producer price growth data to 0.9 percent month-on-month and 6.2 percent year-on-year.

Factory prices were driven in May mainly by the cost of energy, which surged 4.1 percent on the month and 18.2 percent annually. Oil rose on Wednesday to within sight of Monday's record high above $143.

"This confirms that price pressure is mounting in the pipeline, but much of this pressure still seems to be coming from oil. So it is the same old story, just worse," said Holger Schmieding, co-head of Europe Economics at Bank of America.

Core producer price inflation, a measure excluding the volatile energy and construction components, came to 0.3 percent month-on-month and 3.8 percent annually -- against 0.4 percent and 3.7 percent, respectively, in April.