Tesla's sales in key European markets fell again in March, data showed on Tuesday, adding to signs that drivers are shunning Elon Musk's electric car brand as competition from China stiffens and some protest against his political views.

The plan for a day of mass demonstrations follows a series of violent incidents. Anti-Musk activists have been accused of throwing Molotov cocktails at Tesla facilities in Colorado, Nevada and Oregon and defacing Tesla vehicles there, and on Monday, authorities said they found multiple “ incendiary devices ” at a Tesla location in Texas.