Pakistan radio said last night that India had launched an all-out offensive against East Pakistan without a formal declaration of war. This was denied by an Indian Government spokesman, who said that Pakistan Sabre jets intruded into Indian air space and were rebuffed by Indian Gnat fighters. The spokesman also said that Indian troops had strict orders not to cross the frontier, but in Washington official American sources said that two Indian Army brigades had engaged Pakistani forces. At present, they said, there was nothing to indicate that the clash, near Jessore, was anything more than a major frontier incident.

Pakistani estimates of Indian forces committed - nine infantry divisions, four mountain divisions and two tank regiments - are almost certainly exaggerated. The difficulties of deploying a large force in such terrain would be immense, but clearly the two armies have met in battle. General war, long seen as a possibility, might now be unavoidable.