By Kyu-seok Shim

SEOUL, April 20 (Reuters) - North Korean leader Kim Jong Un oversaw Sunday's ballistic missile test launches as part of efforts to evaluate the performance of warheads carrying cluster bombs and fragmentation mines, state media KCNA reported on Monday.

The tests represented the fourth ballistic missile launch this month and the seventh this year, as North Korea seeks to build its missile and nuclear capabilities in defiance of U.N. Security ⁠Council resolutions.

The tests involved five launches of upgraded short-range Hwasong-11 Ra surface-to-surface tactical ballistic missiles to evaluate the power and performance of the new warheads, KCNA said.

North Korea fired the missiles toward an island target zone about 136 km (85 miles) away, striking an area of roughly 12.5 to 13 hectares (31 to 32 acres) with what the report described as high density, demonstrating the system's capability for concentrated suppression strikes.

South Korea on Sunday said North Korea fired the missiles from near the city of Sinpo on its east coast toward the sea at around 6:10 a.m. (2110 GMT on Saturday), with the presidential Blue House urging Pyongyang to stop such "provocations".

A South Korean Unification Ministry spokesperson said on Monday there was "an unusually large presence" of commanders from units on the front line separating the Koreas at the test, linking this to Kim's stated intent to bolster deterrence against South Korea through expanded deployment of tactical missiles. North and South Korea technically remain at war after the 1950-53 Korean War ended in an armistice agreement, not a peace treaty.

KCNA said Kim expressed satisfaction with the test results, calling them proof that years of work by a specialised missile warhead research group had not been in vain, and urged defence scientists to continue advancing technologies needed to strengthen the military's combat readiness.

Images released by KCNA showed Kim and his daughter, believed to be named Ju Ae, watching the launches surrounded by several military officials. It is the latest occasion that Ju Ae has joined her father to witness weapons tests, increasing speculation that she is being positioned as Kim's successor.

Earlier this month, North Korea tested a new cluster-bomb warhead on a ballistic missile and an electromagnetic weapon, in a move that analysts said was part of efforts by Pyongyang to showcase its capacity to fight a modern war.

Britain's Foreign Office condemned North Korea over the latest ballistic missile launch and urged the reclusive nation to engage in meaningful diplomacy.

Lim Eul-chul, a professor at Kyungnam University, said the test showed Pyongyang's intent to strike "more precisely, across a wider area and with far greater lethality," warning that if the missiles are deployed closer to the front line, it could put Seoul and key South Korean and U.S. military bases within range.

The seven-week-old U.S.-Israeli conflict against Iran, which aims to curb Tehran's nuclear and missile programme, may also have reinforced Pyongyang's own ambitions in this area, experts and former South Korean officials said.

In late March, Kim said Pyongyang's status as a nuclear-armed state was irreversible and expanding a "self-defensive nuclear deterrent" was essential to national security.

(Reporting by Kyu-seok Shim and additional reporting by Gursimran Kaur in Bengaluru; Editing by Lisa Shumaker, Ed Davies and Lincoln Feast.)