* STOXX Europe 600 down 0.4 percent amid mixed earnings * AstraZeneca drops, warns of tough year ahead * Ericsson jumps after Q4 results By Tricia Wright LONDON, Jan 31 (Reuters) - European shares fell on Thursday as investors digested mixed earnings reports, with a warning from AstraZeneca knocking its shares while Ericsson surged after fourth-quarter results. The STOXX Europe 600 was down 0.4 percent at 287.44 by 0929 GMT having dropped 0.6 percent in the previous session. But having benefited from a broad shift in investment flows towards riskier assets, the index remains near two-year highs and is on course to notch up a near 3 percent rise in January. On the first big day of the European earnings season, heavyweights AstraZeneca and Royal Dutch Shell came under pressure after releasing disappointing numbers. Ericcson jumped 8 percent on higher-than expected fourth-quarter core profit and revenue growth, raising hopes the world's top mobile telecom gear maker is beginning to shake off the global downturn. Trading volume in Ericcson was robust, at 182 percent of its 90-day daily average, against the STOXX Europe 600 on 33 percent of its average. Strategists and fund managers see further scope for gains in the share market, helped by liquidity support from central banks alongside an improving global economic outlook. "January has been an exceptionally strong month with especially retail money finally leaving cash and the bond markets and flowing into equities. Normally when January does well, so does the whole year so I remain positive," Lex van Dam, hedge fund manager at Hampstead Capital, which manages around $500 million of assets. Philippe Gijsels, head of research at BNP Paribas Fortis Global Markets said: "A lot of people are still quite underinvested... which means that there's quite a bit of money ready to come to these markets. "We have the economic recovery, we have central banks injecting, and I think this bodes well for further returns this year." AstraZeneca skidded 5.1 lower after Britain's second biggest drugmaker said it faced a tough 2013, with earnings set to decline "significantly more than revenue" as operating costs rise. Trading volume in AstraZeneca stood at 137 percent of its 90-day daily average. Oil major Royal Dutch Shell shed 1.3 percent after fourth-quarter results significantly undershot expectations. "Overall, the Q4 results are slightly disappointing but medium-term growth targets are reconfirmed. We expect downward revisions to our forecasts for 2013 (currently EPS 477 cents) and will review our 'hold' recommendation after considering today's disclosures," Liberum Capital said in a note. The broker noted that the shares offer a yield of about 4.8 percent and "robust if unexciting" growth prospects, retaining its view that Shell remains attractive relative to BP.