(Adds closing prices)
* FTSEurofirst up 0.5 pct, fifth straight session of gains
* Stabilisation in oil price lifts energy stocks
* Auto stocks down as JP Morgan cuts China market forecasts
* European bourses in 2015: link.reuters.com/pap87v
* Asset performance in 2015: link.reuters.com/gap87v
By Sudip Kar-Gupta
LONDON, July 14 (Reuters) - European stocks rose on Tuesday as oil prices steadied, supporting energy shares, after first tumbling when Iran and six world powers reached an agreement on Tehran's nuclear programme.
Investors' belief that Greece will pass reforms in order to get a new bailout also enabled European stocks to record a fifth day of gains, even though Greek Prime Minister Alexis Tsipras faces opposition over the austerity plan.
"There's been a lot of progress on Greece after the weekend and that is one of the reasons why traders are continuing to buy into this market," said Thames Capital Markets strategist Nav Banwait.
The STOXX Europe Oil & Gas Index rose 0.8 percent, with Statoil among the best performers in percentage terms on the pan-European FTSEurofirst 300 index.
The FTSEurofirst closed up 0.5 percent at 1,580.34 points, the fifth day in a row in which it has risen.
The euro zone's blue-chip Euro STOXX 50 index advanced 0.5 percent while German internet company United Internet rose 2.9 percent after a price target upgrade from Deutsche Bank.
But carmakers fell as JP Morgan cut forecasts on China's auto market, a day after a profit warning from Brilliance China Automotive Holdings, which makes BMW cars in China.
JP Morgan also reduced its price target on Volkswagen , whose shares declined by 2.1 percent.
The FTSEurofirst is up around 15 percent since the start of 2015 while the Euro STOXX 50 is up 14 percent, with economic stimulus measures from the European Central Bank (ECB) having helped to support markets despite the worries over Greece.
($1 = 0.9059 euros)
Today's European research round-up (Additional reporting by Alistair Smout; Editing by Louise Ireland and Gareth Jones)