MOSCOW, Russia (AP) — A successful Olympics behind him, President Vladimir Putin is facing what may become the most dramatic challenge of his rule: how to respond to the turmoil in Ukraine, a country he has declared vital for Russia’s interests, which is home to millions of Russian-speakers and hosts a major Russian navy base.

Some in Ukraine’s Russian-speaking east and south already have begged the Kremlin to help protect them against what they fear could be violence by the victorious protesters who toppled Ukraine’s Moscow-backed leader. Putin has refrained from taking a public stance on Ukraine amid the Sochi Games, but the mounting tensions could quickly leave him with a stark choice: Stick to diplomacy and risk losing face at home, or open a Pandora’s box by entering the fray.

If Moscow openly backs separatist-minded groups in Ukraine’s Crimean Peninsula that serves as the base for Russia’s Black Sea Fleet, it could unleash devastating hostilities that Europe hasn’t seen since the Balkan wars. And ignoring pleas for help from pro-Russian groups in Ukraine could shatter Putin’s carefully manicured image of the tough ruler eager to stand up to the West, eroding his conservative support base at home, where his foes could be encouraged by the Ukrainian example.

Facing such high risks, Putin has remained silent, weighing his options. His premier, Dmitry Medvedev, yesterday poured scorn on the new Ukrainian authorities who replaced President Viktor Yanukovych, and questioned their legitimacy. But he wouldn’t say what action Russia might take to protect its interests.

“If you consider Kalashnikov-toting people in black masks who are roaming Kiev to be the government, then it will be hard for us to work with that government,” Medvedev said.

The Russian Foreign Ministry criticised the West for turning a blind eye to what Moscow described as the opposition reneging on its agreement signed Friday to form a unity government and aiming to “suppress dissent in various regions of Ukraine with dictatorial and, sometimes, even terrorist methods”.

Amid spiralling tensions and increasingly tough rhetoric, Putin’s best hope for striking a peaceful compromise on Russian interests in Ukraine could paradoxically be former Prime Minister Yulia Tymoshenko, who was freed Saturday after more than 2 1/2 years behind bars.