Four men, a woman and two children were killed and 17 others injured as an improvised explosive device triggered by the United Liberation Front of Asom ripped through a public bus in Upper Assam's Sibsagar district on Thursday.

According to police sources, the IED, placed inside a bag under the third row behind the driver, was triggered by remote control at around 1000 IST.

The bus was travelling from Sonari to Sibsagar when the incident occurred at village Majgaon.

Six of the critically injured were shifted to the Assam Medical College hospital in nearby Dibrugarh district, while the rest were admitted to Sonari and Sibsagar civil hospitals.

A PTI correspondent who visited the site saw bodies strewn 100 metres away from the blast spot.

The incident comes close on the heels of several blasts triggered by suspected ULFA militants.

The ULFA, which was perceived to be on the back foot after Bhutanese Army operations against it in December, has been regrouping in recent months.

It threw bombs on two cinema halls in Tinsukia district, blew up a goods train and blasted a telephone exchange in Sibsagar district in the past one month.

Army, police and intelligence reports have spoken about ULFA's strike force, the 28th Battalion, having been revived in recent months.

With inputs from PTI