In an escalation of the tense situation in the region, North and South Korea exchanged fire over their heavily fortified border on Thursday, the South Korean Defense Ministry said.

South Korea detected a projectile, assumed to be a small rocket, that was fired toward the western province of Gyeonggi, a South Korean Defense Ministry official told CNN.

The South Korean military responded by firing a few dozen shells at the area from which the North Korean projectile was fired, the official said.

Tensions have spiked on the Korean Peninsula in recent weeks after two South Korean soldiers were seriously wounded by landmines in the demilitarized zone.

South Korea has accused the North of planting the mines, an allegation Pyongyang denies.

Seoul vowed a “harsh” response to the land mines and resumed blaring propaganda messages over the border from huge sets of loudspeakers.

The move infuriated North Korea, which called the broadcasting “a direct action of declaring a war.” It threatened over the weekend to blow up the South Korean speakers and also warned of “indiscriminate strikes.”

North Korea pumped its own propaganda broadcasts over the border on Monday, the same day South Korea started military exercises with the United States and other countries. Pyongyang says it views the drills as a prelude to an invasion.

The two sides have exchanged fire in the past at sensitive points. In November 2010, North Korea shelled an island near the countries disputed maritime border, killing two South Korean marines.

They also traded fire in October 2014. A clash took place between patrol boats in the Yellow Sea, and then another flared days later over land after North Korean gunners apparently targeted balloons carrying leaflets critical of the country’s reclusive regime.

CNN