Exchange-traded funds that track the Russian equity market plummeted in premarket trading on Monday, after a new round of sanctions were imposed on Russian entities and individuals. Tensions between Russia and the U.S. were also escalating after a suspected chemical-weapons attack in Syria; U.S. President Donald Trump tweeted that Russia and its president, Vladimir Putin, were responsible for backing Syrian President Bashar al-Assad, and said there would be a "big price... to pay." The VanEck Vectors Russia ETF RSX, -9.86% sank 7% on heavy volume, with nearly a half-million shares exchanging hands before the open. The iShares MSCI Russia ETF ERUS, -11.14% dropped 8.9% before the bell, on volume of nearly 5,000 shares. Separately, the U.S. dollar rose 3% against the Russian ruble USDRUB, +3.7131% hitting its highest level since November. Both equity ETFs struggled throughout 2017, but have rebounded thus far this year. The VanEck fund is up 5.5% in 2018, while the iShares ETF is up 6.6%. The Dow Jones Industrial Average DJIA, +1.38% is down 3.2% year-to-date, while the S&P 500 SPX, +1.54% is off 2.6% and the Nasdaq Composite Index COMP, +2.13% was up 0.2%.