The South Korean military thinks North Korea may be preparing to blow up two rare roads that connect both Koreas.

According to a source from the South Korean military on Monday, the North Korean military is engaging in activities that may indicate plans to blow up the Gyeongeui and Donghae roads.

Last week the general staff department of the North Korean army said the country would cut off road and railway links between the two Koreas and carry out work to fortify the inter-Korean border.

The source said the South Korean military is watching these activities closely and taking steps to ensure the safety of South Korean soldiers and civilians. 

In a statement carried by the North’s state Korean Central News Agency on Wednesday, the general staff department said the North would start work that day to sever the connections and build strong defense structures.

Also on Wednesday, the North Korean military said it had notified the U.S. military by telephone to prevent any accidental clashes near the border.