SEOUL, South Korea — North Korea on Wednesday fired multiple cruise missiles into the sea in its fifth test of such weapons since January, South Korea’s military said, extending a streak in weapons demonstrations that is elevating tensions in the region.

South Korea’s Joint Chiefs of Staff said the South Korean and U.S. militaries were analyzing the launches that were detected in waters northeast of the eastern coastal city of Wonsan. The South Korean military did not immediately provide the exact numbers of missiles fired or how far they flew. It was not immediately clear either whether the missiles were fired from land or from sea assets.

“Our military has increased surveillance and vigilance and is working closely with our U.S. partners and is closely monitoring signs for further activity from North Korea,” the Joint Chiefs of Staff said in a statement.

Experts say North Korea is ramping up pressure on its rivals in an election year in South Korea and the United States with a long-term focus of forcing Washington to accept the idea of the North as a nuclear power and extract security and economic concessions from a position of strength.

North Korean leader Kim Jong Un has also been issuing belligerent statements toward South Korea, including a declaration that he would abandon the North’s long-term objective of reconciliation with its war-divided rival and threatening to annihilate the South with nuclear weapons if provoked. There is concern in the South that Kim may up the ante with a direct military provocation, possibly around the disputed western sea boundary between the Koreas that has been the site of deadly naval skirmishes in past years.

Cruise missiles, which are designed to be highly maneuverable in flight like small airplanes, are among a growing number of weapons North Korea is developing to overwhelm missile defenses, supplementing the country’s vast number of ballistic missiles designed to be fired from land and sea.

The latest launches were North Korea’s sixth missile-launch event this year, including a Jan. 14 test of the country’s first solid-fuel intermediate-range missile, which demonstrated its efforts to advance its weaponry aimed at remote U.S. targets in the Pacific, including the military hub of Guam.

The North earlier this year tested new cruise missiles designed to be fired from submarines and also long-range cruise missiles with the potential to reach U.S. military bases in Japan.

The United States, South Korea and Japan have been strengthening their combined military exercises and sharpening their nuclear deterrence strategies.