MOSCOW (AP) — Having for months dismissed Western sanctions on Russia as toothless, business leaders here are now afraid that the downing of the Malaysian jetliner will bring about an international isolation that will cause serious and lasting economic damage.

Throughout the Ukrainian crisis, U.S. and European sanctions had mainly targeted a handful of individuals, sparing economic ties. Then last week the U.S. imposed penalties on some of Russia’s largest corporations. And when the airliner was shot down just a day later in Ukraine, allegedly by separatists with Moscow’s support, concern grew in Russia that the sanctions would only get worse as President Vladimir Putin shows little sign of cooperation.