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* Q1 EBITDA tops forecasts, debt down 45 pct
* Quarter saw crude hit 13-year low
* Company says investment to spur future profit
* Shares up 3.7 pct vs declining Moscow market
* Vankor oilfield to reduce production in 2016 (Update share price, adds comments, cash flow data)
By Vladimir Soldatkin and Olesya Astakhova
MOSCOW, June 8 (Reuters) - Rosneft's quarterlycore earnings and debt reduction helped lift shares in Russia'stop oil producer on Wednesday despite weak crude prices slashingits net profit.
Led by Igor Sechin, a long-standing ally of RussianPresident Vladimir Putin, Rosneft said its investment in thequarter would help generate future production and profit.
Core earnings - before interest, taxation, depreciation andamortisation (EBITDA) - fell by 14.4 percent to 273 billionroubles ($4.22 billion) but topped the 258 billion expected byanalysts polled by Reuters.
Rosneft cut its debt, generated mainly by a $50 billionacquisition of Anglo-Russian TNK-BP oil firm in 2013, by 45percent to $23.9 billion.
"The results were broadly in line with expectations, whilethe company still managed to generate free cash flow in thefirst quarter despite a 20 percent rise in capex," analystAlexander Kornilov at Moscow brokerage Aton told Reuters.
The company said its free cash flow was 80 billion roublesin the first quarter, down 38.5 percent.
Rosneft's shares were up 3.7 percent at 1510 GMT, reaching amonthly high and outperforming a 0.44 percent decline in Moscowstock market.
Oil prices in the January-March quarter were down by about$20 a barrel from a year earlier, hitting a 13-year low of$27.10 in January and knocking profits across the sector.
Rosneft's net profit fell by 75 percent to 14 billionroubles, missing the 33 billion expected by analysts.
Its peers also suffered, with Rosneft stakeholder BP reporting an 80 percent profit fall and Russian rival Lukoil seeing profits slide by almost 60 percent.
"The decline in first-quarter net income can be explainedmainly by the fact that the company has been in an investmentcycle," Rosneft said.
"The launch of several projects which will help increase oilproduction and therefore secure the net income rise is plannedfor the next reported period," it said.
"It seems they have come to an end of their correctionphase," analysts at investment house ALOR wrote in a note.
"When it comes to buying, Rosneft's shares could berecommended," they said.
Analysts said higher taxes and transportation tariffs hadalso held back Rosneft in the quarter.
Sales fell by 21 percent to 1.05 trillion roubles while Rosneft pumped an average of 4.1 million barrels of oil per day,down 1 percent year on year, the company said.
The company plans to launch new producing projects,including Suzun, later this year to offset decline at otherdeposits. Its relatively new oil field, Vankor, launched in2009, will show a production decline to 21 million tonnes thisyear from 22 million tonnes in 2015, a company official told aconference call.
($1 = 64.6372 roubles) (Additional reporting by Lidia Kelly; editing by Jason Neely)
