Media reports spoke of a spike in activity at the North's Punggye-ri nuclear test site, as quoted by intelligence officials
The vote, clouded by North Korean nuclear threats and a slowing economy, dealt a blow to President Park Geun-Hye
The alleged vote-buying took place in Suwon, 30 kilometres south of the capital Seoul
The drill involving K-9 self-propelled artillery units and 130mm multiple rocket launchers was held in the coastal county of Goseong
Activists used gas-filled balloons to float 100,000 leaflets criticising North Korean leader Kim Jong-un over the heavily militarised border
They released 50,000 leaflets marking the 6th anniversary of sinking of a South Korean warship with the loss of 46 sailors
It also attacked the server of a major software firm specialising in providing security software for Internet banking.
There is already a THAAD battery stationed in Guam and Japan is also considering taking on the system
The allies had been set to sign an agreement today on setting up a joint working group to look into the roll-out of THAAD