North Korea may carry out some sort of provocation following the high profile defection of a senior diplomat and as the joint South Korea-U.S. drill gets underway, a government source said Sunday.

"There is a considerable chance that the North confronted with difficulties may implement some sort of provocation to help rally its people and consolidate the regime's hold on power," an official at Seoul's unification ministry said. Such a move can also divert attention from Pyongyang's other troubles as it struggles with heightened sanctions handed down by the United Nations.

The official, who spoke under condition of anonymity, said there has been a steady spike in verbal attacks launched by the communist regime and that the wording has become more virulent.

"The defection of Thae Yong-ho, the No. 2 man at the North Korean Embassy in London may be causing tremors in the North as well as hurting the country's image abroad," the source said.

He said Seoul is on guard against various developments including attacks carried out on North Korean escapees, the kidnapping of South Korean diplomats and citizens in foreign countries and assassination of prominent anti-North Korean civic group leaders.

The source said Seoul is also keeping close tabs on potential cyber attacks.

There have been reports that Pyongyang has been sending agents abroad to target South Korean nationals. The North has been threatening retaliation for what it calls the kidnapping of restaurant workers in April, and with Thae's defection being confirmed by Seoul last week, it may be more inclined to strike.

The diplomat is reportedly from the very best family in North Korea, which may be a sign that North Korean leader Kim Jong-un's grasp on power is not as strong as it is believed.

Besides such attacks, the start of the joint Ulchi Freedom Guardian drill that kicks off on Monday for a two-week run, could cause the North to lash out.

"The government urges all citizens to be on guard for possible provocations and to cooperate with the government if the need arises," the official said.

Related to the UFG exercise North Korean state-run Korean Central News Agency citing the spokesman Committee for the Peaceful Reunification of Korea claimed that move by the Seoul and Washington to provoke the North will only fuel the will of North Koreans and its military to retaliate if attacked.

The CPRK official said Pyongyang will move forward to build up its nuclear deterrence to counter all threats from abroad. (Yonhap)