The foreign ministers of Kazakhstan, Kyrgyzstan, and Uzbekistan joined senior officials from Tajikistan and Turkmenistan at today's signing.
The new treaty requires the five Central Asian states to ban the production, acquisition, or deployment of nuclear weapons or their components, as well as nuclear explosives.
It also forbids the hosting or transport of nuclear weapons or materials for third parties.
Kazakh Foreign Minister Kasymzhomart Tokaev expressed hope that the deal "could provide an impulse for strengthening nonproliferation [efforts] and help prevent nuclear weapons from falling into the hands of terrorists."
Kimberly Marten of New York's Columbia University has been tracking events in the former Soviet Union for years. She says governments in predominantly Muslim Central Asia have been eager to signal their opposition to radical elements.
"For all of them, there is a sense that by saying, 'You can't get nuclear weapons here, we're not interested in having nuclear weapons,' they are distancing themselves from any possible terrorist groups," Marten says. "And that's very important to them, because many people have seen Central Asia as a possible location for the war on terror. And by demonstrating that they are not on the side of terrorists, that they have no interest in helping terrorists, they are again sort of stating that they are on the right side in this battle."
The signing was selected to coincide with the 15th anniversary of the closing of the Semipalatinsk nuclear-test range.
Rustem Tursunbaev, vice president of the Nevada-Semipalatinsk movement that was formed in the last years of the Soviet Union, insists the new treaty's significance extends far beyond Central Asia. His group allied antinuclear activists from the USSR and the United States, drawing its name from primary nuclear testing sites in their respective countries.
"The signing of the agreement on a nuclear-[weapon]-free zone in Central Asia is a remarkable, unbelievable moment [and] event -- not just for Central Asia, but for the whole world," Tursunbaev says.
The location for the signing -- Semipalatinsk -- serves as a reminder that the agreement is more than simply symbolic. And that it is arguably about more than just security.
Semipalatinsk was the Soviet Union's main testing site for nuclear weapons, with some 500 nuclear devices detonated there between 1949 and 1989.
"Kazakhstan was obviously a real victim of nuclear development in the sense that they have so much territory that was harmed by fallout; they have many health problems in outlying areas today that are still a result of the developments that happened during Soviet times," Professor Marten says. "And so I think that there's an environmental statement that is part of this process and not merely one that involves security issues."
Shortly after independence in 1991, Kazakhstan voluntarily gave up the nuclear arsenal it inherited from the Soviet Union. Other countries, particularly the United States, have hailed that decision and cited Kazakhstan as a model for others, like Iran and North Korea, to follow.
The United Nations has been urging governments in the region to sign a nuclear-weapon-free treaty for more than a decade. Fears have been widespread of rampant nuclear proliferation following the breakup of the Soviet Union and the resulting shock to its military and nuclear complex.
Central Asian leaders -- Kazakh President Nursultan Nazarbaev and Uzbek President Islam Karimov, in particular -- spent a decade calling for such a treaty.
Marten says that while none of the Central Asian states appears to be developing nuclear weapons, the treaty has added value for the five signatory states.
"This is not an unexpected development, and it's been a very important sign of the ability of the Central Asian states to cooperate with each other at an institutional level," Marten says. "And there is a great deal of support for the idea that only by cooperating together can they solve their economic problems and their environmental problems."
The deal clearly states that its signatories are permitted to harness nuclear energy for peaceful purposes. Kazakhstan and Uzbekistan are the only two of Central Asia's five post-Soviet states that have their own nuclear power programs.
(Merhat Sharipzhan of RFE/RL's Kazakh Service contributed to this story.)