At least nine people were shot dead and some others wounded by a group of unknown gunmen on buses in Ghana's Upper East Region, an official confirmed to Xinhua late Thursday.

The victims came under attack while travelling from Bawku, a restive urban community in the Upper East Region, to a market center in neighboring Burkina Faso, said Zubeiru Abdulai, district chief executive of Pusiga.

"The traders were in a convoy with police escort due to armed attacks in and around Bawku when unknown gunmen suddenly opened fire on the buses at close range around Pusiga, leaving nine persons dead and others wounded," said Abdulai.

The official said the security services responded swiftly and have launched a search for the attackers while beefing up security.

No group has yet claimed responsibility for the attack.