WASHINGTON — Even as the international effort to destroy Syria’s vast chemical weapons stockpile lags behind schedule, a similar American-backed campaign carried out under a cloak of secrecy ended successfully last week in another strife-torn country, Libya.

The United States and Libya in the past three months have discreetly destroyed what both sides say were the last remnants of Col. Muammar al-Qaddafi’s lethal arsenal of chemical arms. They used a transportable oven technology to destroy hundreds of bombs and artillery rounds filled with deadly mustard agent, which American officials had feared could fall into the hands of terrorists. The effort also helped inspire the use of the technology in the much bigger disposal plan in Syria.

Since November, Libyan contractors trained in Germany and Sweden have worked in bulky hazmat suits at a tightly guarded site in a remote corner of the Libyan desert, 400 miles southeast of Tripoli, racing to destroy the weapons in a region where extremists linked to Al Qaeda are gaining greater influence. The last artillery shell was destroyed on Jan. 26, officials said.

As Libya’s weak central government grapples with turmoil and unrest, and as kidnappings and assassinations of military and police officers accelerate in the country’s east, American and international weapons specialists hailed the destruction of the Libyan stockpile as a bright spot in an otherwise gloomy security environment.