By Ole Petter Skonnord

OSLO, July 25 (Reuters) - Aluminium producer Norsk Hydro NHY.OL met forecasts with a jump in second-quarter underlying profit on Tuesday and said sanctions imposed on Qatar had a limited effect on its activities there.

Norsk Hydro and Qatar Petroleum QATPE.UL co-own the Qatalum smelter where shipments were disrupted last month as a result of sanctions imposed by the United Arab Emirates, Saudi Arabia, Bahrain and Egypt.

The plant, which produces more than 600,000 tonnes of primary aluminium per year, could not ship through the UAE port of Jebel Ali and had to find alternative routes. It currently ships via Oman.

Norsk said it had seen "limited effect from imposed sanctions on Qatar" and that Qatalum's second quarter results were up due to higher aluminium prices.

Norsk Hydro's underlying earnings before interest and taxes rose to 2.9 billion crowns ($362.75 million) from 1.6 billion and compared with the 3.0 billion crowns forecast by analysts in a Reuters poll.

Its shares were down 3.6 percent at 0952 GMT, lagging an Oslo benchmark index .OSEBX up 0.02 percent.

"I suppose it is a disappointment over our Rolled Products unit," Chief Executive Officer Svein Richard Brandtzaeg told Reuters.

Rolled Products reported an underlying earnings of 84 million crowns, lagging a 189 million forecast, and down from 242 million in same quarter last year, due to some operational problems.

"But we have a plan to fix it," Brandtzaeg said.

Nevertheless there would be some negative impact in third quarter as well, Hydro said.

Other divisions, Bauxite and Alumina, which are used to make aluminium, and Energy also came in below forecast, while its biggest unit, Primary Metal, was above forecast.

Total revenues and net underlying profit were above forecast.

The company has seen its share price rise 50 percent over the past year partly due to rising global demand for the metal.

Norsk Hydro said it had benefited from higher aluminium prices in the quarter.

It repeated its forecast for 4-6 percent global demand growth in aluminium, adding that the market was largely balanced, and said cost cuts of 500 million crowns for the year were on track.

"We only expect minor changes to consensus estimates," said Hjalmar Alberg, an analyst at Kepler Cheuvreux.

($1 = 7.9944 Norwegian crowns)

(Additional reporting by Gwladys Fouche; editing by Jason Neely and Louise Heavens) ((gwladys.fouche@tr.com; +47 23 31 65 94; Reuters Messaging: gwladys.fouche.reuters.com@reuters.net; Twitter handle: @gfouche))