On 23 November North Korea shelled the island of Yeonpyeong, killing at least four South Koreans. The disputed border area has been the scene of numerous clashes in the past.
Won Sei-hoon, director of South Korea's National Intelligence Service, told a parliamentary committee behind closed doors that the recent attacks came amid "internal complaints" about Pyongyang's third generation succession and worsening economic situation, according to a ruling party official.
"There is a high possibility that the North will make another attack," South Korea's Yonhap news agency quoted him as saying, adding that the government was trying to burnish the credentials of the designated leader who was still very young and untested, and also win new concessions from the international community.
South Korea is building up defences on Yeonpyeong island, but some senior officials have told the BBC they hope Mr Won is wrong and the worst of the current crisis is over.
"There will be ongoing measures as you said to beef up our forces including the stationing of new weapons, upgrading our marines on Yeonpyeong island but I think on this particular crisis we are reaching the apex and we will see a gradual de-escalation," said Chung Min Lee, ambassador for international security affairs.