Seoul - South Korean media called on Monday for Seoul to consider building its own nuclear weapons amid growing doubts over its decades-old alliance with Washington following North Korea's sixth nuclear test.Pyongyang on Sunday triggered global alarm with by far its most powerful test to date, after it claimed it had successfully tested a hydrogen bomb that could be mounted onto a long-range missile, which analysts say is a major advancement in its nuclear programme.The South, which hosts 28 500 US troops to defend it from the North, is banned from building its own nuclear weapons under a 1974 atomic energy deal it signed with the US, which instead offers a "nuclear umbrella" against potential attacks.READ: UN Security Council to meet on North Korea nuclear testBut growing nuclear and missile threats from its belligerent northern neighbour is prompting some in the South to call for its own nuclear armament."As nuclear weapons are being churned out above our heads, we can't always rely on the US nuclear umbrella and extended deterrence," the mass-circulation Donga Ilbo newspaper said in an editorial on Monday.The US stationed some of its atomic weapons in the South following the 1950-53 Korean War, but withdrew them in 1991 when the two Koreas jointly declared they would make the peninsula nuclear-free.That pact was no longer binding, the editorial said, and added: "There is no reason for us to cling onto the declaration when it has become the 'denuclearisation of South Korea', not the denuclearisation of the Korean peninsula."The Seoul government should not "hesitate" in reintroducing US tactical nuclear weapons as well as building its own atomic devices.'Stop attacking'Following Sunday's test, South Korean President Moon Jae-In called for discussions on deploying "the strongest strategic assets of the US military", without elaborating on what those weapons could be.But Moon's office later clarified that Seoul "maintains" its position on denuclearisation.Analysts warn that growing doubts over the alliance, fuelled by rash comments from US President Donald Trump, could force the South to seriously consider nuclear armament."Undermining alliance solidarity at this moment is dumb and dangerous," tweeted Colin Kahl of Georgetown University, who worked for the Obama administration.In a series of tweets posted hours after the test, Trump denounced the North but also criticised Seoul, saying: "South Korea is finding their talk of appeasement with North Korea will not work, they only understand one thing!"South Korea is finding, as I have told them, that their talk of appeasement with North Korea will not work, they only understand one thing!— Donald J. Trump (@realDonaldTrump) September 3, 2017 On the campaign trail, Trump had accused US allies including Japan and South Korea of not paying enough for their defence and suggested they develop their own nuclear weapons, triggering major concerns about the alliance.Trump must "stop attacking" the allies and tweeting before meeting them, Kahl said, adding: "The Administration needs to speak with one voice before confusion splits the US from its allies, produces a war, or both."