President Asif Ali Zardari has said that Pakistan's armed forces are vigilant and ever ready to respond to any challenge to national sovereignty and territorial integrity and also fully prepared to defeat terrorists.He was addressing the induction of two newly built warships PNS Babur and PNS Hunain in the Pakistan Navy fleet in Karachi on Defence Day today.He said the induction of both warships in Pakistan Navy will significantly increase the maritime security of the country.The President said a strong navy guarantees the security of the sea borders. Asif Ali Zardari expressed gratitude to Turkish and Romanian governments for their cooperation.Source: Radio Pakistan