At least 17 people have drowned in northern Ghana in recent weeks after nearby Burkina Faso opened spillway gates to dams following heavy rains, the country's relief agency said on Friday.

"As at yesterday, the death toll in the three northern regions stood at 17 and a number of farmlands have been destroyed," National Disaster Management Organisation (NADMO) spokesman Nicholas Mensah told AFP.

He said while the area was already flooded due to torrential rains that have pounded the area recently, the situation was worsened when Burkina Faso released water from its overflowing dams. Burkina Faso authorities opened the floodgates on August 10.

"We have had lots of rains up north. Burkina Faso has also experienced the same pattern of rain and they are spilling water from their dams," he said.

"That has exacerbated the problem we have already been having with rainfall," he added.

Burkina Faso had alerted Ghana of its plans and the agency told people in the most vulnerable areas to move," said Mensah.

Torrential rains have killed more than 30 people in southern Ghana, including in the seasside capital Accra, in what experts described as the worst floods in a decade.