The victims, all mobile phone traders, were returning to Zamfara state capital Gusau late Saturday after the wedding of a colleague in neighbouring Sokoto state when they were seized, a union leader and a security source said.
They were captured after one of their four vehicles broke down.
"Thirty of our members were abducted yesterday while returning from the wedding of our colleague in Sokoto," Kabiru Garba Mukhtar, the head of mobile traders union in Zamfara said.
"The kidnappers called me on the phone belonging to one of the victims, confirming they are holding 30 of our colleagues."
Heavily armed criminal gangs, known locally as bandits, are ravaging parts of northwest and central Nigeria, raiding villages and carrying out mass kidnappings for ransom despite military operations against them.
The convoy of 50 wedding guests had stopped at Lambar Bakura village after one of the four buses they were driving in broke down, which was when their captors attacked them, said a security source in the region.
"Twenty managed to escape while 30 were kidnapped," said the security officer, who asked not to be identified as he was not authorised to speak on the incident.
Police in Sokoto and Zamfara did not immediately respond to AFP inquiries on the incident.
Northwest and central Nigeria is a hub of criminal gangs who attack villages and highways, killing and abducting residents and drivers and looting and burning homes.
Last week, 58 residents were kidnapped when gunmen invaded Kwari village in nearby Katsina state, according to local officials.
The criminal gangs who the government has officially declared terrorists maintain camps in Rugu forest, straddling Zamfara, Katsina, Kaduna and Niger states.
The gangs are driven by financial motives, but security sources say they are increasingly forging alliances with jihadists from the northeast waging a more than decade-long insurrection.
Since last year, they have also carried out attacks on schools, kidnapping students to squeeze ransom from the authorities and the parents of their victims.
In one high-profile attack in March, gunmen blew up a rail track between the capital Abuja and northwestern Kaduna city, before kidnapping scores of passengers from the halted train.