* Sees 2016 investments at NOK 135 bln, down c10 pct vs 2015
* Sees investments falling further in coming years
* 2016 oil output seen at 1.53 mln barrels/day
* 2016 gas output seen at 106.6 bln cubic metres (Adds detail)
STAVANGER, Norway, Jan 14 (Reuters) - Investments inNorway's key oil and gas sector will fall further in 2016 and inthe coming years following a 16-percent drop in 2015, theNorwegian Petroleum Directorate (NPD) said on Thursday,suggesting more pain ahead for the country's economy.
Norway's economy, long one of Europe's best performers, hasbegun to struggle as its main industry, oil production, is hitby a three-quarters fall in the price of Brent crude since June 2014.
The NPD now sees investments, excluding exploration, fallingto 135 billion crowns ($15.3 billion) in 2016 from close to 150billion in 2015. It predicted a moderate rebound in investmentsfrom 2019 onwards.
Its 2016 investment forecast was revised down from anestimate of 137 billion made a year ago, echoing recent forecastcuts by the central bank and Statistics Norway.
"They (investments) are expected to continue their declinegoing forward, followed by a moderate increase from 2019," theNPD said in a statement.
The directorate noted, however, that its current investmentforecasts presume the oil price will increase from today's levelin the near future.
"If this presumption proves wrong, and oil prices remain atthe current level for a longer period, this could entail furtherpostponement of activities, resulting in even lower investmentsand exploration costs," it said.
In terms of production, Norway's oil output will drop to1.53 million barrels per day in 2016 and 1.41 million in 2020from 1.57 million in 2015, the NPD estimated.
Norwegian gas production will fall to 106.6 billion cubicmetres in 2016 from last year's 117.2 billion, rising again to111.1 billion by 2020, it said.
The directorate said low prices led to oil companies notdeveloping certain hydrocarbon fields. More than half ofNorway's oil and gas resources have yet to be produced.
"We see a tendency for the companies to prioritiseshort-term earnings rather than long-term value creation," NPDchief Bente Nyland said in a statement.
On the positive side, the directorate said oil firms'efforts to cut costs led to more oil development projectsbecoming more profitable.
Norway's top oil producers include Statoil, Shell, ConocoPhillips, BP, Det norske and Lundin Petroleum.
($1 = 8.8169 Norwegian crowns) (Reporting by Stine Jacobsen, writing by Gwladys Fouche;Editing by Terje Solsvik and Mark Potter)
