Over the past two months the west has nervously watched events in Ukraine, hoping the country might step back from the brink. On Tuesday, those hopes received a severe blow on the streets of Kiev. In clashes between Ukrainian government forces and opposition protesters, at least 26 people were killed and more than 240 injured. With violence breaking out elsewhere, there are fears that Ukraine – a nation of 46m sitting on a faultline between western and eastern Europe – may be sliding towards civil war.

It is still not clear who triggered the brutal clashes in the capital. In recent weeks, violence has been committed not only by the security forces loyal to President Viktor Yanukovich but also by opposition protesters who are disaffected by his corrupt government and want him to quit. But whatever the cause, there is every reason to be alarmed by this sudden turn of events. Ukraine peacefully separated from the dying Soviet Union in 1991 and seamlessly moved to independence. In every crisis since then – most notably the Orange Revolution of 2004 – it has resolved conflict without bloodshed. This time, the country risks turning into a powder-keg at the heart of the continent.

Ukraine’s present plight is largely the fault of President Yanukovich. True, he came to power in broadly fair elections in 2010. But egged on by Vladimir Putin, Russian president, he has committed a string of mistakes that undermine both his authority and his legitimacy. Last November he walked away from signing an association agreement with the EU, enraging millions of Ukrainians who want closer ties with the west. He then tied Ukraine to a $15bn loan from Mr Putin, using force to try to quell public anger. Amid the turmoil, he has never negotiated with the opposition in good faith. After this week’s violence, it is impossible to treat him as anything other than an international pariah.