Large-scale police operation against illegal migration is taking place in downtown Sofia and several other places across Bulgaria on Friday morning.

There is heightened police presence in the area of the Maria Luisa boulevard and Lavov most (Lions' bridge) in the centre of the Bulgarian capital, which is a popular gathering place for migrants.

At present, the interior ministry refuses to disclose any further information, noting that the results of the operation will be announced later on Friday, private bTV station informs.

Speaking to the Bulgarian National Television (BNT), Interior Minister Rumyana Bachvarova explained that this is a routine specialised operation which is conducted periodically whenever it is deemed necessary.

Authorities are checking for illegal migrants in the interior of the country, which is part of Bulgaria's approach to tackling the migrant pressure.

Bachvarova noted that the approach to tackling the refugee influx involves control at the entry and exit points as well as in the interior of the country.

The operation carried out on the order of the interior ministry's chief secretary, Georgi Kostov.

Participating officers from border police, migration directorate, Sofia directorate of the interior ministry and eleven other regional directorate of the ministry.

Police is conducting checks of hotels, hostels and other places of accommodation as well as vehicles and various retail establishments.