Violence has escalated in oil- and timber-rich Assam in recent months after talks between representatives of the ULFA and the Indian government failed to make headway.
Two people were killed and 10 others wounded on Friday in a bomb blast at a crowded bus station in Guwahati.
Earlier in January, 72 labourers, migrants from a different Indian state, were killed by armed men suspected of being ULFA seperatists.
The earlier attack prompted a visit to the region by India's prime minister.
Separatist attacks have killed more than 20,000 people since they began in 1979.
The ULFA want Assam to become independent from India.