On a tip off, the police halted the bus coming from Dola to Guwahati in Tinsukia town and recovered the four hand-made IEDs last night, district SP Arnab Deka said.
After investigation, the driver and handyman of the bus were arrested, Deka said.
The explosives were suspected to be of the Paresh Baruah ULFA-I faction as the insurgent outfit was attempting to transport IEDs for subversive activities, he said.