South Korea has fired warning shots at a suspected North Korean drone flown across the DMZ.
Soldiers fired about 20 rounds before the craft turned back, Yonhap news agency said citing South Korean officials.
Earlier, South Korea’s President Park Geun-hye urged China to impose the strongest possible sanctions against North Korea, following its apparent nuclear test.
North Korea claims it has tested a hydrogen bomb.
That claim is doubted by experts, who say the blast, though probably nuclear, was not big enough to have been a thermonuclear explosion.
In her annual press conference, President Park Geun-hye said the international community’s response to North Korea “must differ from the past”, without giving details.
China, North Korea’s closest ally, has repeatedly condemned North Korea’s nuclear tests but is often accused of doing little to try and stop them.
Park Geun-hye stressed China’s past statements but added: “I am certain that China is very well aware if such a strong will isn’t followed by necessary steps, we will not be able to stop the North’s fifth and sixth nuclear tests and we cannot guarantee true peace and stability on the Korean peninsula.”
“I believe the Chinese government will not allow the situation on the Korean peninsula to deteriorate further.”
Last week Secretary of State John Kerry also urged China to take a tougher line, telling his Chinese counterpart the relationship with North Korea cannot be “business as usual”.
President Park Geun-hye also spoke about the steps South Korea was taking with the US to “neutralize North Korea’s provocative actions” including additional deployments of American military assets on the Korean peninsula.
Answering a question about whether Seoul would consider ending its involvement in the jointly-run Kaesong industrial zone, just north of the border, Park Geun-hye said its future depended on Pyongyang’s actions.
Seoul has already limited access to Kaesong from South Korea, to only those directly involved in its operations.