South Korea fired warning shots after a drone suspected to be from North Korea entered the demilitarised zone on Wednesday, local media reported. 

The drone returned to North Korea after at least 20 warning shots were fired, South Korea's Yonhap News Agency reported. 

"The unidentified aerial vehicle appeared in the skies above the Mount Dora Observation Post at 2:10 pm, and the military responded with warning broadcasts and shots before the vehicle immediately returned to the north," said Seoul's Joint Chiefs of Staff. 

Tensions between the two Koreas, which are technically still at war, escalated after North Korea announced the testing of a hydrogen bomb last week. 

Following the H-bomb claim, South Korea resumed loudspeaker broadcasts along the border, criticising North Korean leader Kim Jong-un.

North Korea resorted to the same tactic, and also scattered leaflets across the border.