* STOXX down 0.8 pct, DAX down 1.5 pct
* Siemens falls after revenues miss
* Amundi a bright spot after strong profits
* GAM sinks further after halting dealing in some bond funds (Adds closing prices)
By Helen Reid
LONDON, Aug 2 (Reuters) - A selloff in European shares extended on Thursday with Germany's DAX taking the brunt of anxieties over trade tensions, while results from industrial group Siemens disappointed but Europe's biggest asset manager, Amundi, impressed the market.
The pan-European STOXX 600 fell 0.8 percent to a one-week low as investors sold risky assets on President Donald Trump's threat to increase U.S. tariffs on Chinese imports.
Germany's top index, the most sensitive to trade, dropped 1.5 percent as heavyweights like Siemens tumbled.
"Stocks which disappoint are being penalised by the market, but I think beyond actual earnings delivery, the market is concerned about tariff uncertainty," said Emmanuel Cau, head of European equity strategy at Barclays.
Siemens, which makes everything from turbines to trains, fell 4.7 percent after reporting lower than expected revenues, though its profit slightly beat expectations.
Analysts and traders said the fall was probably due to concerns over the new "Vision 2020+" strategy and disappointment that the company did not increase its earnings forecasts.
The autos sector, which has suffered in recent weeks from the U.S. threats to impose more tariffs, fell 1 percent.
BMW outperformed, ending down 0.4 percent, after it reported a smaller-than-expected 6 percent decline in second quarter operating profit. It also brushed off concerns about new anti-pollution rules and global trade tensions which caused rival Daimler to warn on profits.
Daimler fell 1.4 percent.
Cau has an "overweight" recommendation for autos, highlighting that car volumes are still going up and margins are resilient even though investors are shunning the sector due to the tariff fears.
"The sector might be a proxy to express concern about tariffs, but it is already down very significantly and you can pay very little to still buy interesting growth," he said.
France's Amundi jumped 5.4 percent after reporting higher second-quarter profits, benefiting from an inflow of new client money. "Amundi reported a good-quality beat to consensus expectations on higher revenues and inline costs," said UBS analysts.
Shares in German retailer Metro rose 9.7 percent after it said steps to stabilise its shrinking Russian business are starting to pay off.
Many more stocks were punished for disappointing results.
Shares in Altice Europe, the debt-ridden telecoms and cable group, sank 16.3 percent after reporting that margins suffered when it pushed on with aggressive promotions in France in the second quarter.
Hugo Boss shares fell 7.8 percent after earnings missed forecasts. "The 2 percent EBITDA miss is likely to be taken negatively in light of concerns that Hugo Boss' strong underlying retail performance is not translating to an improvement in margins," said Berenberg analysts.
Overall companies in the MSCI Europe index have so far reported year-on-year earnings growth of 8.2 percent for the second quarter. European earnings growth pales in comparison with that delivered by U.S. firms, however.
Bringing up the rear among European stocks was Swiss asset manager GAM, sinking 14.9 percent - taking its losses since Tuesday to 26 percent.
An investor exodus after it decided to suspend a director forced the firm to halt dealing in some bond funds.
"The suspension of client dealings in absolute return bond funds increases the likelihood of a bear case scenario for AuM (assets under management) loss," said Baader Helvea analysts.
Reporting by Helen Reid, additional reporting by Danilo Masoni; Editing by Alison Williams