* FTSEurofirst 300 down 0.1 pct
* Greek stocks down 15 percent since start of week
* ARM gains after Apple results
* Lanxess, Nordea rally after results (Updates with closing prices, adds quite)
By Alistair Smout and Blaise Robinson
LONDON/PARIS, Jan 28 (Reuters) - Greek stocks slumped further on Wednesday as concerns mounted about the banking sector after the election victory of anti-bailout party Syriza and the new government's cancellation of privatisation plans.
Other European stocks made marginal gains overall, but there were some upbeat corporate earnings reports and tech companies received a boost from Apple's robust profit growth.
Athens' ATG share index was down 9.2 percent and the Greek banking index skidded 27 percent, hitting a record low, amid investor fears that the new government's anti-austerity stance would make negotiations with the euro zone on a new aid deal difficult and jeopardise liquidity, traders said.
The ATG has now lost 15.4 percent since the start of the week, in the wake of Syria's election victory on Sunday, while the banking index has plummeted 98.7 percent since late 2009, before Europe's sovereign debt crisis started.
International investors have cut their exposure to Greek banks since then. The combined market value of Greece's top four - Alpha Bank, Piraeus Bank, National Bank of Greece and Eurobank Ergasias - has fallen to about 11 billion euros ($12.5 billion).
"It would be mainly Greek private investors. A lot of it has to do with capital flight, which is relentless," said Phoebus Theologites, chief investment officer at SteppenWolf Capital.
"Brokers also report that a lot of large, institutional investors - pension funds and index trackers - are also selling Greek stocks across the board today."
Shares in Greek utility PPC and Piraeus Port Authority tumbled by 13.9 percent and 7.3 percent respectively after the new government said it would stop the planned sale of a 67 percent stake in Piraeus Port Authority.
Energy Minister Panagiotis Lafazanis told Greek television earlier that PPC's planned privatisation would also be halted.
The FTSEurofirst 300 index of top European shares was down 0.1 percent at 1,474.99 points, steadying after U.S. stocks opened higher.
Wall Street was boosted by forecast-beating results from Apple, which also lifted shares in European technology firms.
ARM Holdings, which supplies chip designs for Apple, rose 1.7 percent after Apple posted quarterly results that smashed Wall Street expectations with record sales of big-screen iPhones in the holiday shopping season and a 70 percent rise in China sales.
Peripheral euro zone indexes underperformed core euro zone indexes such as Germany's DAX, up 0.8 percent, and bourses outside the currency area, which were lifted by encouraging corporate earnings.
Germany's Lanxess surged 7.6 percent in afternoon trade after the world's largest maker of synthetic rubber said that 2014 adjusted core earnings exceeded its expectations.
Shares in Sweden's Electrolux were among the top gainers, rallying 12.1 percent after the global home appliances maker forecast decent market growth on both sides of the north Atlantic this year.
Nordea, the Nordic region's biggest bank by market value, also surged, by 8.8 percent after it reported fourth-quarter operating profit in line with expectations on Wednesday and raised its dividend.
So far in Europe's earnings season, about 5 percent of STOXX 600 have reported results, of which 69 percent managed to meet or beat analyst forecasts, according to Thomson Reuters StarMine data. That has fuelled hopes of a long-awaited recovery in European earnings.
Today's European research round-up (Editing by Mark Heinrich)