This went for really long. One of bad days in the West w.r.t internet outages.
For now from their replies to their customers as reported on NANOG mailing list - issue was because of flowspec rule.
Hello everyone,
From the last couple of hours there is a high noise ongoing on the outage mailing list (which is a bit focused on outages within the US) about Century Link / Level3 AS3356 outage.
As of now people are reporting of outage + fact that stale routes are still visible. Level3 is one of the upstreams of many Indian networks like Airtel AS9498, Jio AS64049, Sify AS9583 etc. Besides a lot of downstreams behind AS3356.
Details about the outage are not very clear so far but likely limited to US and Europe. Expect issues in connectivity with content and eyeballs in those regions.
--