Photographs recently released by the Yemeni government suggest that an interdiction last month by the United States Navy and Yemen’s security forces seized a class of shoulder-fired antiaircraft missiles not publicly known to have been out of state control.

Such missiles, in the hands of militants, would pose new threats to military and commercial aviation and would mark an escalation in illegal arms trafficking in the Arabian Peninsula. Yemen has asserted that the missiles were bound for rebels in the country’s northwestern frontier, and both the United States and Yemen have suggested that the shipment may have come from Iran.

The missiles were displayed this week to journalists in Yemen, along with other weapons and military equipment that the Yemeni authorities said had been seized from the Jeehan 1, a dhow that was boarded at sea on Jan. 23.

The photographs and accompanying video images are grainy, but they show either modern Chinese- or Iranian-made heat-seeking missiles in their standard packaging. The weapons are of a class known as Manpads, for man-portable air-defense systems, of which the best known example is the American-made Stinger.

Matthew Schroeder, an analyst who follows missile proliferation for the Federation of American Scientists in Washington and the Small Arms Survey in Geneva, said that while a definitive identification was not yet possible from the information released, the missiles appeared to be either QW-1M missiles from China or Misagh-2 missiles from Iran.

“If these missiles are indeed one of these systems and were bound for an armed group, this is a significant development,” he said.

Many questions remain about the seizure, which Yemen said also included small arms ammunition, ground-to-ground rockets, explosives, military-grade binoculars and more.

Neither Yemen nor the United States has fully described the boarding of the dhow, including how it was detected or the precise roles of the security services and vessels that were involved. The dhow’s shipping documents, if they exist, have also not been made public, nor has any information obtained from the vessel’s navigation devices, logbooks or charts.

The seizure follows past joint operations by Yemen and the United States, including American Navy Tomahawk missile strikes against reputed Al Qaeda encampments in 2009 about which the governments issued false or misleading statements.

Investigations by members of the Yemeni Parliament and by Amnesty International later found that in one of those attacks, many civilians had been killed by American-made BLU-97 cluster munitions. The United States has not taken responsibility for the deaths or fully acknowledged its role, raising questions about the Pentagon’s honesty and transparency regarding its security collaboration with Yemen.

The antiaircraft missiles, as shown, included missile tubes and battery units, but not the trigger assemblies, known as grip stocks, necessary to fire the weapons.

The Yemeni authorities said they believed the missiles were destined for the rebels, known as the Huthis, who control a de facto statelet in northwestern Yemen, along the Saudi border. They also have a growing following, and are widely viewed as a threat to Yemen’s efforts to build a more unified nation after the uprising and political crisis of 2011.

The Huthis fought an intermittent guerrilla war against the Yemeni government from 2004 to 2010, gaining combat experience and building up supplies, including munitions obtained from Yemen’s corrupt military. They also briefly fought the Saudi military. Yemen has a vast supply of unregulated weapons and is a hub of regional arms trading.

The Huthis are Zaydis, followers of a variant of Shiite Islam, and they make up about a quarter of Yemen’s population. That sectarian affiliation — however distant — with Iran’s mainstream Shiite population has been the basis for repeated accusations of Iranian influence over the Huthis. Iran’s support appears to be ideological rather than military, and its extent is unclear.