Police say gunmen have killed at least seven passengers in an attack on a bus in southern Pakistan.

Officer Javed Ahmed said separatists were suspected in the ambush Friday in remote Kazi Ahmed district in Sindh province.

Sindh is home to small separatist groups that have engaged in low-level violence before, but attacks of this nature are rare.

Ahmed said several other people were wounded in the incident.

Pakistan is battling violence from Islamist insurgents based in the northwest. There is also a violent separatist movement in Baluchistan, which borders Sindh.