* Higher oil prices, production boost GDP
* Growth expected to slow in H2
By Martina Fuchs
DUBAI, Oct 20 (Reuters) - Saudi Arabia's gross domestic product, unadjusted for inflation, jumped 26.1 percent from a year earlier to 1,022.2 billion riyals ($273 billion) in the first half of this year on the back of higher oil output and energy prices, official data showed.
The GDP of the oil sector alone soared 38.9 percent to 573.4 billion riyals, the country's Central Department of Statistics and Information said on Thursday. It did not release figures for inflation-adjusted GDP growth; Saudi Arabia's consumer price inflation was 5.3 percent in September.
"Brent oil prices are high compared to the first six months of 2010, when they were running at around $80. In the first six months of 2011, Brent was running at around $115 and $120," said James Reeve, senior economist at Samba Financial Group in London.
"Most of the increase in nominal GDP will be oil prices and production," he said, adding that oil output jumped 8.5 percent in the first half compared to the same period in 2010.
Saudi Arabian purchasing manager data for September suggested the economy lost some momentum in the third quarter of this year, with business activity in the non-oil private sector slowing to its lowest level since the data series was launched in August 2009.
Liz Martins, senior MENA economist at HSBC in Dubai, said she expected a slowdown in the second half of the year. "But growth for the year as a whole will still be one of the highest rates in the region."
Analysts polled by Reuters in September predicted the Saudi Arabian economy would expand by an inflation-adjusted 6.2 percent this year and 4.5 percent in 2012 .