European shares retreat at the open, trade tensions bite

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LONDON, Sept 5 (Reuters) - European shares opened lower on Wednesday as continuing trade tensions and spreading worries about emerging market currencies cut investor appetite for risky assets.

At 0728 GMT, the pan-European STOXX 600 was down 0.4 percent, with losses spread across industry sectors and trading centres.

A number of corporate announcements triggered strong swings, notably in BioMerieux.

The French pharmaceutical group was the best performer on the index, up 8.3 percent after better than expected first-half results and a raised 2018 outlook.

In the same sector, Bayer fell 3 percent after reporting a disappointing 3.9 percent gain in underlying core earnings for the quarter.

Another French firm was also among the highest risers. Outdoor advertising group JCDecaux added 6.8 percent after a rating upgrade by BofA Merrill.

Snuff and cigar maker Swedish Match fell 5.2 pct after an institutional investor sold a stake of 4.3 million shares at a discount. (Reporting by Julien Ponthus; Editing by Catherine Evans)