China and the United States said Tuesday they have busted an international arms trafficking ring and arrested 26 suspects, in a rare instance of law enforcement cooperation.

The arrests came after a 10-month investigation triggered by the seizure of a parcel containing pistols and rifle parts at the Shanghai international airport in August last year, China's public security ministry said.

A Chinese man was detained when he tried to collect the parcel, which had come from New York and was destined for the eastern Chinese province of Zhejiang, the ministry said.

Subsequent investigations revealed a 25-year-old Chinese man living in the United States since 2009 had been shipping firearms to Chinese buyers contacted online using courier services.

Authorities have seized 93 guns, more than 50,000 bullets and a large number of gun parts in China. Among those arrested was a staff sergeant with the US National Guard who had 12 guns in his possession when he was picked up in May.

He was allegedly planning to ship the guns to China, where possession of firearms is prohibited and punishable by jail.

US officials travelled to Shanghai where they were allowed "unprecedented access to investigative information" the US embassy in Beijing said in a statement.

It said the success of the joint operation was "a sign of optimism" that could "lead to even greater law enforcement cooperation in the future" -- a sentiment echoed by Beijing.

The latest arrests came after China and US authorities smashed a network of child pornography sites August last year, with Chinese police arresting several people suspected of money-laundering and maintaining the sites in China.