Two US police officers have been shot outside the Ferguson police department, local media reports.

St Louis County Police Chief Jon Belmar said gunfire hit one of the officers in the face and another in the shoulder.

Both are being treated after suffering “very serious gunshot injuries,” he added.

The town has been the scene of demonstrations since August 2014, when an unarmed black teenager was killed by a white police officer.

Witnesses say gunfire could be heard as a protest took place outside the Missouri police station.

La police de #Ferguson confirme 2 officiers blessés par balle. Devraient survivre. (photos LaurieSkrivan) pic.twitter.com/LTSklYHeXX— Breaking 3.0 (Breaking3zero) March 12, 2015

A few dozen demonstrators had gathered in the area after police chief Thomas Jackson announced he would be resigning.

‘Widespread racial bias’

Police Chief Jackson’s resignation will take effect from March 19, 2015. The city announced it would be giving Jackson a severance