New Delhi, Oct. 2 -- Russian President Vladimir Putin has warned that Moscow would respond with "all weapons" at its disposal if NATO were to directly attack Russian territory, escalating an already tense exchange between Moscow and the Western military alliance over the strategic Baltic exclave of Kaliningrad.

Putin, speaking at a foreign policy forum on Thursday, reiterated that Russia does not intend to attack European countries. But he said Moscow would respond forcefully to any aggression and accused European governments and NATO of raising tensions by preparing for a possible confrontation with Russia.

The warning came days after Moscow sent a written message to NATO alleging that the alliance was preparing an air and naval blocka...