Police arrested the leader of a small Zambian opposition party on Wednesday on charges of defaming President Edgar Lungu by describing the head of state as a dog, his lawyer said.

Chishimba Kambwili, leader of the National Democratic Congress (NDC), defended his comments as he was led by officers, telling journalists that his statement in an online video had been misunderstood.

Kambwili and other opposition politicians have accused Lungu of cracking down on dissent - a charge regularly dismissed by the government which says it protects free speech.

The arrest came two days after the state Registrar of Societies cancelled the registration of the NDC - saying its constitution was flawed and effectively shutting it down. Kambwili has said he will challenge the decision in court.

"The arrest is a clear sign of intimidation, coming shortly after the de-registration of Kambwili's party. The ruling party seems to be very uncomfortable with Kambwili," Lee Habasonda, a political analyst at the University of Zambia told Reuters.

Kambwili's party broke away from the Lungu's Patriotic Front (PF) in 2016 and took its first seat in parliamentary elections in April in the government's copper-producing heartland.

"The allegation is that he made references to dogs from Chawama" in the video, his lawyer Christopher Mundia told Reuters, referring to a township where Lungu previously lived and served as member of parliament.

"The police have drawn inference that he was referring to the head of state as a dog from Chawama and that is why they have decided to charge him with defamation of the president," Mundia said.

Kambwili told journalists his statement in the local Bemba language has been misunderstood, but did not explain what he meant.

Police released a statement saying Kambwili had been detained, but did not go into further details. There was no immediate comment from the government.