* FTSEurofirst 300 up 0.1 pct
* Greek stocks down 15 percent since start of week
* ARM gains after Apple results
* Lanxess, Nordea rally after results (Adds detail, updates prices)
By Alistair Smout and Blaise Robinson
LONDON/PARIS, Jan 28 (Reuters) - Greek stocks continued to slump on Wednesday, on mounting concerns about the banking sector in the wake of anti-bailout party Syriza's victory in Sunday's election and after the new government cancelled privatisation plans.
Other European stocks made marginal gains overall, but there were some upbeat corporate earnings reports and tech companies got 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, as investors feared 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 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 the country's banks since then. The combined market value of the top four Greek banks Alpha Bank Piraeus Bank National Bank of Greece Eurobank Ergasias has fallen to about 11 billion euros ($12.5 billion).
"Should their collateral be disqualified by the ECB, they will have no money, and a bank with no money is not a bank ... The price is just building in the expectation that things could go pretty badly," said Simon Maughan, head of research at OTAS Technologies.
"A lot of local and retail punters ... will be looking at the price action and wanting to get out, at any price."
Shares in Greek utility PPC and Piraeus Port Authority fell by 14.5 percent and 10.4 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.
At 1518 GMT, the FTSEurofirst 300 index of top European shares was up 0.1 percent at 1,476.59 points, turning positive 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 2.1 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 8.4 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 12.3 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 6.7 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, fuelling hopes of a long-awaited recovery in European earnings.
Today's European research round-up (Editing by Catherine Evans and Susan Fenton)