The plot thickens, this will be an interesting one to watch.

Considering they are coming from the Chinese side, and we all know china. It could very well have been flares/rockets from a military exercise you will never hear anything about. It could be fireworks, flares or lanterns from a village celebration, wedding, funeral practices, harvest celebrations etc.

The part that makes me think it isn't something ET, is it's stated they seem to be coming from the Chinese side of the border, again similar explanations can be applied to the Indian side, but a "Chinese Lantern" would likely hang around visible for several hours.