Opposition activists had called for demonstrations in the Central Asian country's largest cities, including Astana, Almaty and Karagandy, to protest a controversial proposal for land reforms that includes extending land leases for foreigners.
Authorities had rejected all applications to hold protests on Saturday and cordoned off the main squares of Almaty and Astana, while activists called on their supporters to protest nonetheless.
In Almaty, the country's largest city, some 100 people took to the streets.
Kazakhstan's deputy prosecutor general, Andrei Kravchenko, said that as of today, 40 people had been arrested for organising and taking part in these unauthorised demonstrations, TASS news agency reported.
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A number of journalists were briefly detained during the protests. Kazakh police later said that the arrests had been a "misunderstanding," Interfax news agency reported.
In April demonstrators had taken to the streets in a string of provincial towns to protest proposed land reforms the government says are important to attract investment into the country.
President Nursultan Nazarbayev earlier this month halted the proposal, saying that "doubts had arisen in society."
A combination of inflation and falling real incomes have fuelled social discontent in a country often regarded as a regional success story despite endemic corruption.
Land policy is highly politicised in ex-Soviet Central Asia where privatisation policies of the 1990s are often recalled with bitterness and where nearby China is seeking to expand its agricultural interests.