India and Pakistan both said they shot down each other’s fighter jets on Wednesday, a day after Indian warplanes struck inside Pakistan for the first time since a 1971 war, prompting world powers to urge restraint.

Both countries have ordered air strikes over the last two days, the first time in history that two nuclear-armed powers have done so, while ground forces have exchanged fire in more than a dozen locations.

Tension has been elevated since a suicide car bombing by Pakistan-based militants in Indian-controlled Kashmir killed at least 40 Indian paramilitary police on Feb. 14, but the risk of conflict rose dramatically on Tuesday when India launched an air strike on what it said was a militant training base.