A South Korean naval ship fired warning shots after a North Korean patrol boat crossed a disputed sea border off the peninsula's west coast and fired shots back before retreating, a South Korean defence official said.
There were no casualties on the South Korean side, he told Reuters.
The area has been the scene of clashes in the past that killed scores of sailors on both sides, with North Korean vessels frequently crossing the so-called Northern Limit Line, which it refuses to recognise as a maritime border.
North Korean officials visiting the South in a surprise trip have agreed to a second round of high-level talks.
The agreement came after the country's unofficial second most important leader after Kim Jong-un on a rare trip to South Korea for the close of the Asian Games.
The North Korean delegation was led by Hwang Pyong-So, the top political officer for the Korean People's Army. The rivals held their highest level face-to-face talks in five years.
A young American man has been caught trying to swim across a river to North Korea, according to South Korea's Yonhap news agency.
The report cites a government source as saying that the man was arrested while swimming across the Han River, which borders the two countries.
The Pope posed and smiled for a selfie with a young Catholic in South Korea.Read the full story ›
Vast crowds gathered in Seoul's Gwanghwamun Square in South Korea as Pope Francis delivered a beatification mass for 124 Catholic martyrs.
Beatification is the last step before sainthood in the Roman Catholic Church.
In his homily before a crowd of hundreds of thousands, Francis said the martyrs' courage and charity and their rejection of the rigid social structures of their day should be an inspiration for people today.
Pope Francis was greeted by cheers and the waving of handkerchiefs as he arrived at South Korea's Daejeon World Cup Stadium to hold a mass.Read the full story ›
Pope Francis has surprised South Koreans during his visit to the country by shunning an expensive luxury car to travel in a compact car instead.
After arriving at the airport he climbed into the backseat of a a Kia Soul - the manufacturer's second smallest model.
Pope Francis has refused to use a bullet-proof "popemobile" like his predecessors in favour of low-key cars.
His choice of car has received wide coverage in South Korea, where ostentatious shows of wealth usually represent a person's status.
Pope Francis has arrived in South Korea on the first papal visit to the Asian nation in 25 years, stepping off a plane on to a red carpet and greeting the president, Catholics and grieving relatives of the recent ferry disaster.
During his five-day visit, Francis plans to beatify 124 Korean martyrs and encourage a vibrant and growing local church seen as a model for the future of Catholicism.
North Korea has fired three "short-range projectiles" into the sea, just an hour before Pope Francis arrived in South Korea for an official visit, Associated Press have reported.
An official with the South Korean Defence ministry said the apparent test firing Thursday came less than an hour before rival Seoul welcomed the pope for the first papal visit to South Korea in 25 years.
The official says that the projectiles were fired from Wonsan on the east coast and flew about 220 kilometers (135 miles).
The official spoke on condition of anonymity, citing official policy.
Young survivors of the South Korean ferry disaster have begun giving testimony at the trial of the 15 crew members charged with abandoning the sinking ship.
The children, whose identities have been protected, said they were repeatedly told to stay in their cabins when the ship began to take on water.
"We were waiting and, when the water started coming in, the class rep told everyone to put on the life vests ... the door was above our heads, so she said we'll float and go through the door and that's how we came out," one of the teenagers said.
Others told the hearings that coastguard officials waited outside the stricken ferry for passengers to swim out rather than go into the ship to try and rescue them.
"We said to ourselves, 'why aren't they coming in?'" one said.
The crew members on trial, including the captain, have said they thought it was the coast guard's job to evacuate passengers. Video footage of their escape triggered outrage across South Korea.