All parade grounds in Assam where official Independence Day celebrations will be held on August 15 are being put under round the clock vigil by security personnel to thwart possible attempts by the banned United Liberation Front of Assam to plant explosive devices.

Police informed that separate arrests of at least five ULFA militants last week at Dibrugarh, Sivasagar and Guwahati along with deadly explosives exposed the banned outfit's plan to disrupt official celebrations of Independence Day so that it could hog international media glare.

Police, quoting confessions made by arrested ULFA militants, informed that Prabal Neog, commander of the 28th battalion of the outfit, had issued orders to lower rank cadres to carry out subversions on I-Day especially in Upper Assam areas and Judges' Field in Guwahati, the venue for state-level celebrations of the I-day.

This has prompted the police to beef up security arrangements in and around all the parade grounds in the state and metal detectors is being used to scan nooks and corners of such grounds.

The ULFA is known to be in possession of programmable timer device that can be attached with powerful improvised explosive devices so that the same could be planted much in advance of the intended date of explosion.

Sivasagar police arrested two ULFA cadres Amal Bora and Moneswar Payeng on late Friday night. During the interrogation, the due revealed the ULFA's design to trigger blasts in Upper Assam parade ground on Independence Day.

Another two ULFA militants -- Ridumsa Mushahary alias Siphung and Uday Das --confessed before the police that they had sneaked in the capital city with a plan to plant explosives in the Judges' Field.

The police arrested the ultras from Garobasti under Dispur police station on Friday night along with three bombs, two detonators, a switch of a timer device and a mobile phone. Two other ULFA members were arrested by Guwahati police on the same night. They were identified as Mrinal Kalita and Dhireswar Deka hailing from Tulsibari in Rangiya in Kamrup district.