KAMPALA, May 4 (Xinhua) -- Seven people were killed and 13 others critically injured on Monday when a passenger bus collided head-on with a trailer in northern Uganda, police said.

The crash occurred when the bus traveling from the district of Arua to the capital Kampala collided with the South Sudan-registered trailer at Labok village, along Nwoya-Pakwach highway at 1:15 a.m. local time (2215 GMT), police traffic and safety spokesperson Michael Kananura told reporters.

There were 67 passengers in the bus, police said.

"Preliminary investigations indicate that the bus driver attempted to overtake two other buses ahead of him and in the process he collided head-on with an oncoming trailer," Kananura said.

"As a result, four passengers died instantly at the scene and 16 others were injured and rushed to Anaka hospital. Three additional victims later succumbed to their injuries, bringing the death toll to seven," he said. ■