Seven persons were injured when a bomb planted by a woman ULFA cadre posing as a patient exploded at a diagnostic centre on Thursday, shortly after the army seized an IED from tracks at the local railway station.

Police said the woman left two packets of potato chips and a gift-wrapped package on a seat in the lounge of the privately owned Sanjeevani Diagnostic Centre after collecting a medical report.

Patients and staff on duty presumed she was a patient.

The IED concealed in the package exploded shortly thereafter, injuring seven persons and destroying the centre's cash counter and smashing glass panes, police said.

The seriously injured, included two employees of the centre and two patients, were admitted to the Assam Medical College Hospital in Dibrugarh.

The centre's owner, Rameswar Bahiti, a Hindi-speaking person, was targeted by the ULFA, police said.

Earlier in the day, the army found a powerful IED near the Sibsagar railway station and defused it.

Defence sources said the IED was found by an army patrol near the railway station when passengers were waiting to board morning trains. An army bomb squad defused the device.

Police and army launched a search operation in upper Assam following these incidents.