An elderly man talks with a policeman near the checkpoint in Kumanovo, Macedonia. May 10, 2015. [Photo/Agencies]

KUMANOVO - Sporadic gunfire could be heard in an ethnic Albanian suburb of northern Macedonia on Sunday, after a day-long gun battle between police and an 'armed group' killed six policemen and wounded about 30.

The Interior Ministry said a sixth policeman had died overnight in hospital. It said an unspecified number of gunmen were killed but gave no information on civilian casualties during the clashes that began in the town of Kumanovo, 40 km (25 miles) north of the capital Skopje, early on Saturday.

The government proclaimed two days of national mourning.

A Reuters photographer said Kumanovo was tense but relatively calm on Sunday, with sporadic gunfire.

A police source said police were "still trying to break the remaining elements of the terrorist group".

Police said on Saturday they had acted on information about an "armed group" and launched an operation in an ethnic Albanian district of Kumanovo, in a region that saw heavy fighting during an ethnic Albanian insurgency in 2001.

Units of special police in armoured vehicles locked down the neighbourhood and helicopters circled overhead. A Reuters photographer reported hearing heavy automatic gunfire and loud explosions. Black smoke rose over the town and residents were seen leaving the area carrying belongings.