* STOXX 600 down 0.16 pct
* Ryanair jumps after union agreement
* Autos stocks suffer as tariffs kick in (Adds closing prices)
By Helen Reid
LONDON, Aug 23 (Reuters) - European shares gradually fell into the red on Thursday after the latest round of U.S.-China tariffs hurt trade-sensitive autos stocks and sentiment suffered as Wall Street indexes slipped into negative territory.
The STOXX 600 edged down 0.16 percent to 383.42 points, with most European bourses posting only modest losses.
The United States and China implemented 25 percent tariffs on $16 billion worth of each other's goods on Thursday, bringing to $50 billion the value of imports subjected to tariffs on either side since early July, with more in the pipeline.
Autos stocks were the worst-performing for a second day and lost 1.4 percent.
On Wednesday a surprise profit warning from tyre maker Continental sank the stock and hit the sector, already one of the worst impacted by tariff fears.
Continental fell a further 4.3 percent, bottom of the DAX, taking its losses over 15 percent since Wednesday's open.
Carmakers Daimler, BMW and Volkswagen fell by 0.6 to 1.6 percent, while Peugeot, Michelin and Renault were the biggest CAC 40 fallers, down 3.2 percent, 2.2 percent and 1.8 percent respectively.
Overall shares continued to move in a range that is unsettling some investors concerned about complacency in the market.
"We have not witnessed (or not yet) a sudden evaporation of risk appetite, as happened, for example, after the summer of 2015, the last time that the health of the world economy was truly in debate," said ODDO BHF economists.
"Corrections and turbulence in recent months and weeks have been fairly localised in both space and time."
Strong earnings growth is part of what is preserving the market. With the second-quarter results season tailing off, MSCI Europe firms have reported 10.9 percent year-on-year earnings growth.
Swiss telecoms group Sunrise Communications rose 7.2 percent after it increased its guidance for full-year 2018 EBITDA.
Outside trade war moves, shares in budget airline Ryanair jumped 5.5 percent after the Irish pilots' union Forsa said it had reached an agreement in a labour dispute.
Danish medical equipment, supplies and distribution company Ambu posted the worst performance of the STOXX 600 index and sank 12 percent after its third-quarter results missed analysts' targets.
Shares in Swiss asset manager GAM fell 4.8 percent. The stock is down 23 percent since July 31, when it suspended a director, halting dealing in some bond funds soon afterwards.
Austria's Raiffeisen Bank, which operates across eastern Europe and has been in the firing line as new U.S. sanctions on Russia develop, fell 4.2 percent.
Reporting by Helen Reid and Julien Ponthus; Editing by Janet Lawrence