Kaduna state police said gunmen armed with "sophisticated weapons" attacked the two churches in Kurmin Wali, a forest community in Afogo ward, at 11.25am on Sunday.
They said officers were still trying to confirm how many people were taken.
A police spokesperson said the area was remote and difficult to reach due to bad roads, making it challenging to obtain reliable information in the immediate aftermath of such attacks.
The chairman of the Christian Association of Nigeria in the northern part of the country, Reverend John Hayab, told Reuters by phone that 172 worshippers were kidnapped, and that nine later escaped, leaving 163 still held.
"Information came to me from the elders of the churches that one hundred and seventy-two worshippers were abducted while nine escaped," Hayab said.
Initial figures in Nigeria often vary widely after mass kidnappings.
Security agencies typically give conservative early numbers while local community and religious groups sometimes cite higher tallies.
A similar pattern occurred during the abduction at a Catholic school in Kaduna State in a previous incident.
Police said troops and other security agencies had been deployed to the area and that efforts were under way to track the abductors and rescue the captives.
Northwest Nigeria has registered a surge in mass kidnappings by armed gangs operating from forest enclaves, attacking villages, schools and places of worship.
Similar attacks on churches have sparked allegations of the persecution of Christians by US President Donald Trump and some US politicians.
The US government launched military strikes in Sokoto on December 25, allegedly targeting an Islamic State group in the region.
with AP
