Police have kept cordoned off the Nayapaltan central office of the BNP since Saurday morning.
Hundreds of policemen and plainclothes intelligence officers, equipped with armoured personnel carriers, water canons and prison vans, started gathering in front of the BNP office since this early morning.
BNP leaders and activists alleged that the party central office was virtually cordoned off Saturday morning as nobody was allowed to get into and come out of it.
However, police denied the allegation of laying siege to the BNP office and said they only beefed up security to avert any unpleasant incident.
BNP claims that police have detained three activists of their party while they were trying to enter in to the office.
Earlier, BNP sought the authorities' permission to hold a rally at the Suhrawardy Udyan on January 7 marking the lopsided 5 January general elections of 2014 which they are observing as ‘Democracy Killing Day’.
But the permission has not been given by the police.
The BNP had then requested to police to hold a rally in front of its Naya Paltan headquarters on Saturday, but is yet to secure a clearance.
Police have taken a vigilant watch to confront any probable untoward situation as there is no permission for the party to hold any rally, a police official said.