Park made the remark when she presided over a meeting with foreign affairs and security-related ministers as Pyongyang has churned out near-daily threats of war on the Korean Peninsula, according to presidential spokesman Yoon Chang-jung.
"Though it is a must to strike back strongly in the event of North Korean provocations, what is just as important is for us to keep North Korea from even harboring provocations through strong diplomatic and military deterrence," Park said during the meeting, according to Yoon.
Park also said the current security situation is "grave."
In recent weeks, North Korea has sharply ratcheted up tensions with repeated war threats in anger over joint South Korea-U.S. military exercises as well as a new U.N. Security Council resolution adopted in response to its third nuclear test on Feb. 12.
Pyongyang voided the Korean War armistice and nonaggression pacts it signed with South Korea decades ago and cut off all cross-border hotlines before declaring over the past weekend that it was in "a state of war" and threatened to close a joint factory park in the North Korean border city of Kaesong.
On Tuesday, the North said it will restart a plutonium-producing nuclear reactor and other facilities at its Yongbyon complex in order to help address power shortages and to "bolster up the nuclear armed force both in quality and quantity till the world is denuclearized."
Spent fuel rods from the 5-megawatt reactor can yield weapons-grade plutonium, if reprocessed.
An official at South Korea's presidential office said that the country is closely watching whether Pyongyang will take concrete steps to put the reactor back on line. It could take some time to restart the reactor as preparatory measures are necessary, such as fabricating fuel rods, the official said.
Despite the North's harsh rhetoric, analysts believe that chances of war breaking out on the peninsula are extremely low, because the communist regime in Pyongyang is well aware that any war would be suicidal.
Still, South Korea's military -- supported by the U.S. -- remains on high alert, with its top leaders vowing to sternly retaliate if attacked by the North.
During a defense ministry policy briefing on Monday, Park ordered the military to deal sternly with any North Korean provocations without "political considerations," saying she takes "very seriously" a recent string of North Korean moves and war threats.
In Tuesday's meeting, Park and the top security officials had "in-depth" discussions on the situation in North Korea and in the Kaesong Industrial Complex as well as reactions from the international community, the military's readiness and other related issues, Yoon said.
The meeting was the first of its kind since Park took office in February. Participants included the chief of the national security office, the defense minister, the unification minister and the National Intelligence Agency chief and the first vice foreign minister.
Foreign Minister Yun Byung-se is away on a trip to the United States.
Yoon said Park plans to hold such a security meeting as often as necessary.
At the start of the meeting, Park said she spoke by phone with Peruvian President Ollanta Humala earlier in the day about economic cooperation and other issues, saying the South American nation has always supported Seoul's policy on North Korea.
The 1950-53 Korean War ended in a truce, not a peace treaty, leaving the two Koreas still technically at war. About 28,500 U.S. troops are stationed in South Korea to deter North Korean provocations.