Indi a on Monday voiced its worries over the underground nuclear test carried out by North Korea, saying it is a "development of serious concern". "It is a development of serious concern. India is against nuclear proliferation," Defence Minister A K Antony told reporters soon after taking charge of the Defence Ministry for a second term. He was asked how India viewed the announcement by North Korea that its has "successfully" conducted one more underground nuclear test on May 25 as part of the measures to bolster its nuclear deterrent for self-defence. The first nuclear test was conducted by North Korea in 2006, triggering widespread international consternation and slapping of sanctions against it. Mr. Antony, 68, also spoke of the security situation in India's neighbourhood. "The security scenario around India is becoming more and more challenging. Developments around us is a cause of serious concern to us. So, eternal vigilance is a must from all quarters. "Further strengthening of the national security apparatus will be my topmost priority," he said.