At least four members of a marriage party were killed and seven others grievously injured Monday when the vehicle they were travelling in met with an accident in West Bengal's Siliguri, police said.The accident happened in Matigara in Siliguri when the vehicle, with 15 people returning from a marriage ceremony, collided with another vehicle.According to Siliguri Deputy Police Commissioner O.G. Pal, of the seven injured, the condition of three was critical.