Naval ships of the two Koreas traded warning shots near their western sea boundary after a patrol ship of the Democratic People's Republic of Korea violated the disputed maritime border, Seoul's Defense Ministry said on Tuesday.

The exchange of shots came after high-ranking DPRK officials visited the Republic of Korea on Saturday to attend the closing ceremony of the Incheon Asian Games. During the surprise visit, the DPRK officials agreed to hold another round of senior-level dialogue with the ROK, raising hopes for a reconciliatory mood on the Korean Peninsula.

In Tuesday's sea incident, one DPRK patrol ship sailed around 1 km south of the Northern Limit Line at about 9:50 am, violating the disputed western sea border, an ROK Defense Ministry official told Xinhua via phone.

An ROK guided missile patrol gunboat warned the DPRK ship to return to its territorial waters, but the DPRK ship didn't move until the ROK ship fired warning shots with its machine gun.

The DPRK ship fired back at the ROK ship, which in response fired its machine guns at the DPRK ship. The DPRK patrol ship then returned north.

Neither warship aimed gunfire directly at the other, and no casualties were reported from the ROK ship.

The ROK military strengthened its monitoring of DPRK forces, fully preparing for possible provocations from the DPRK, the official said.

Three days earlier, three high-ranking DPRK officials made a surprise visit to the ROK port city of Incheon for the closing ceremony of the 17th Asiad.

Hwang Pyong-so, the DPRK's second in command, led the delegation that included Choe Ryong-hae and Kim Yang-gon, secretaries of the Central Committee of the Workers' Party of Korea.

During a meeting with their ROK counterparts, the DPRK officials agreed to a second round of high-level talks between late October and early November.

Seoul and Pyongyang had vice-ministerial-level dialogue in mid-February, the first high-level talks since ROK President Park Geun-hye took office in February 2013. There have been no such talks since then amid escalating tensions on the Korean Peninsula.

Park took a cautious stance on expectations for a reconciliatory mood between the two Koreas, saying on Monday that the inter-Korean relations repeated a "vicious cycle of cooling ties ever after inter-Korean contacts".

Even after the February dialogue, the DPRK test-fired ballistic missiles and threatened a "new form" of nuclear test in protest against joint military exercises between the ROK and the United States.

Tuesday's incident occurred in waters near Yeonpyeong Island, a hot spot on the Korean Peninsula.

In November 2010, the DPRK fired artillery shells at the island, killing two civilians and two soldiers.

On Sept 19, one fishery inspection boat of the DPRK violated the Northern Limit Line and returned to the north after warning shots from the ROK.

On May 22, DPRK naval ships fired several rounds of shells toward waters near the Northern Limit Line and two rounds fell near an ROK patrol ship sailing in the waters.