Quite Possible Reasons:
1. Routing is messed up (but that should affect downloading too in most cases).
2. Network Congestion (Quite Possible since, ISPs in India are more concerned about Downloading and doesn't concern about Uploads).
It applies to Airtel, Hathway, DEN or any other ISP who are still in 20th Century.
Good Thing: You don't have to worry about it though if the issue is within the India itself because if it's commonly happening on all the servers (unlike one specific), a lot of consumers will complaint and eventually their Level 2 or Route Team will be notified (if they have any, their nodal team is unresponsive).