ISLAMABAD - Pakistan has showed serious concerns at the recent Indian tests of a Submarine Launched Ballistic Missile and development of a nuclear submarine fleet.

The New Indian Express reported last week that India has reportedly conducted a secret test of the nuclear-capable undersea ballistic missile, code named K-4.

The submarine-launched ballistic missile (SLBM) was test-fired from INS Arihant at an undisclosed location in the Bay of Bengal, the daily said.

Pakistan Foreign Ministry spokesman termed the Indian move as serious developments, which impact the delicate strategic balance of the region.

"The reported Indian tests have resulted in the nuclearization of the Indian Ocean, which should be a very worrisome development for the region and the international community," spokesman, Nafees Zikria said at weekly briefing Thursday.

"The reported SLBM test was not notified to Pakistan," Zikria said.

He said any missile test, whether launched from the surface or submerged platform, can be mistaken by the other country as an offensive missile.

"We, therefore, believe that in line with the spirit of the agreement on the pre-notification of test launch of ballistic missiles, the test should have been notified to Pakistan," he said.

The Vice-Admiral of the Indian Navy, H.C.S. Bisht, has been quoted by the Indian media as saying the INS Arihant is now undergoing sea acceptance trails as it had already passed several deep sea diving drills. He further said the submarine will be commissioned after completing all the sea trials.