Image copyright AFP Image caption The object flew over the demilitarised zone, the border that separates the two Koreas

South Korea says an object which drifted over the border from North Korea on Tuesday appears to have been a balloon carrying propaganda leaflets.

South Korean troops fired about 90 machine gun rounds towards the flying object.

North Korea has flown drones over the border in the past and the incident came at a time of high tension around the heavily guarded border.

The South said the balloons were likely to have come from inside North Korea.

South Korean activists have often flown balloons carrying anti-Pyongyang propaganda messages and light goods like snacks in to North Korea, to the frustration of the South's authorities.

But defence ministry spokesman Moon Sang-Gyun said the object on Tuesday had been spherical, not cylindrical like activists' balloons.

'Destabilising behaviour'

South Korea's new president Moon Jae-in said last week that there was a "high possibility" of conflict breaking out at the border.

The pace of North Korean missile tests has increased in recent months and experts fear it indicates progress towards Pyongyang's ultimate goal of putting a nuclear warhead on a missile that could strike the continental US.

On Sunday, North Korea said it had carried out a "successful" test of a medium range ballistic missile.

That came a week after North Korea tested what it said was a new type of rocket capable of carrying a large nuclear warhead.

The UN Security Council held a closed-door meeting on North Korea on Tuesday evening. In a statement on Monday, it agreed to "take further significant measures including sanctions" to force North Korea to end its "highly destabilising behaviour".

But North Korea's historic ally and main trade partner China said the priority was to push for diplomatic talks.

China's UN Ambassador Liu Jieyi said: "There is no reason why dialogue is not taking place in the current situation," and he stressed all progress in the past "was achieved as a result of dialogue".