Moscow will respond “harshly,” “quickly” and “asymmetrically” to foreign provocations, Putin told an audience of Russia’s top officials and lawmakers.
He added that he “hoped” no foreign actor would cross Russia’s “red lines,” according to a Reuters translation.
Russian President Vladimir Putin has warned the West not to cross a "red line" with Russia and condemned what he called a coup plot against Belarus.
The warning came in his annual state of the nation address, amid heightened tension with the West over Ukraine and jailed Putin critic Alexei Navalny.
"The use of unjust sanctions is growing into something more dangerous: a coup attempt in Belarus," he said.
He backs Belarusian President Alexander Lukashenko, who faces huge opposition.
On 17 April the Belarusian authorities announced that they had foiled a US-backed plot to assassinate President Lukashenko. Russia's Federal Security Service (FSB) said it had detained two Belarusians allegedly involved in the plot.
The coup claim was dismissed by the exiled Belarusian opposition leader Svetlana Tikhanovskaya as a "provocation".