The shelling and the South's forceful response are an escalation of tensions between the two Koreas whose leaders have traded harsh words lately.
South Korea's military said that residents of two islands -- Yeonpyeong and Baengnyeong -- were ordered into shelters due to shelling by the North on Friday morning. The North fired roughly 200 shells near the Yellow Sea islands between 9 a.m. and 11 a.m., which landed on the North Korean side of the maritime border, the South's Joint Chiefs of Staff said in a news release. No casualties were reported.
In response, South Korea conducted a firing exercise at 3 p.m. local time.
The South accused the North of escalating tensions in the wake of the cancellation of an agreement signed in 2018 to reduce military activities, such as surveillance, near their shared border.
Friday's exchange of fire marked the end of a period of calm along the inter-Korean border, said South Korean Defense Minister Shin Won-sik, calling the North's shelling "a provocative act that threatens peace on the Korean peninsula and raises tensions."
Shin added that the South would establish "a strong basis for peace through strength" that would prevent North Korea from carrying out any further aggressive acts.
Yeonpyeong has been a recurrent hotspot over the years. In 2002, six South Korean sailors died in a battle with North Korea's navy. In 2010, four South Korean civilians died in a shelling attack by the North.
Relations between the two Koreas have been frozen in recent years, with no high-level dialogue or cooperative projects taking place.
In a meeting with senior military commanders on Monday, North Korean leader Kim Jong Un said that the Korean Peninsula is "inching closer to the brink of armed conflict" and that peaceful unification with the South was no longer possible.
In a New Year's address, conservative South Korean President Yoon Suk Yeol vowed to "completely block" North Korea's nuclear and missile threats.
Since taking office in 2022, Yoon has spoken harshly about North Korea and argued that the South needs to buttress its own military strength, as well as its defense cooperation with main ally, the U.S.
North Korea has continued to expand its own military and in recent months carried out its first successful launch of a spy satellite. This week, Kim Yo Jong, an influential official and sister of the nation's leader, issued a statement in which she mocked what she called Yoon's "maniac attitude for confrontation."
She also sarcastically "thanked" Yoon for providing the North with a new impetus to build up its armaments.