The defense ministry lashed out at a Catholic priest Sunday for defending North Korea in its attacks against South Korea three years ago, saying his remarks were an affront to the military and the victims' families.

Park Chang-sin, a senior Catholic priest, claimed during a sermon on Friday that North Korea should open fire if South Korea and the United States continue to hold joint military exercises near the South's western maritime border with the North, called the Northern Limit Line (NLL).

He then said that was the case with North Korea's shelling of the South Korean border island of Yeonpyeong in November 2010. Four South Koreans, including two civilians, were killed in the attack.

The sermon was part of a special mass arranged by Catholic priests to demand the resignation of President Park Geun-hye over the state's alleged intervention in last year's presidential race.

The presidential office and the ruling Saenuri Party have openly expressed their displeasure at the priests' move.

Despite their shared last name, the priest and the president are not related.

On Sunday, the defense ministry issued a statement condemning the priest's remarks.

"(The remarks) justify North Korea's provocation, demoralize the (public) sense of national security and the military, and exert a bad influence on our people's will to defend the NLL," the statement said. "It is an irrational act that should never happen, and insults the soldiers and civilian victims who dedicated themselves to national security as well as their families."

In his sermon, the priest also claimed that it is hard to believe that the South Korean warship that sank in March 2010 was torpedoed by the communist country.

Referring to those remarks, the ministry stressed that the sinking was an illegal provocation by North Korea, which claimed the lives of 46 South Korean soldiers in the torpedo attack.

Police, meanwhile, said they have launched a search for a man who claimed to have planted two sticks of dynamite at Myeongdong Cathedral in central Seoul earlier in the day.

The man, presumed to be in his 40s or 50s, made the claim in a phone call to the police, but no explosives were found at the cathedral, police officials said.

"We are considering the possibility that (the threat) was made by someone who took offense at the (priest's) remarks," a police official said, speaking on the condition of anonymity. (Yonhap News)