Karim Massimov's detention was announced by the National Security Committee, which Mr Massimov chaired until he was removed this week by President Kassym-Jomart Tokayev.

Twenty-six demonstrators and 18 security forces personnel died and more than 4,400 people were arrested in days of protests in the largest city Almaty and across the country, the interior ministry said on Saturday.

Mr Tokayev spoke to Russian President Vladimir Putin in a "lengthy" phone call, according to the the Kremlin, and told him the situation was stabilising.

In a statement on the website of the Kazakhstan president, Mr Tokayev told Mr Putin that his country was still being subjected to "terrorist" attacks in some places.

Russia is among a number of countries that are part of the Collective Security Treaty Organisation (CSTO) of ex-Soviet republics that have provided troops to help restore order.

The protests began in response to a near doubling of the price of liquefied petroleum gas which is widely used to power cars in the country.

Mr Tokayev has blamed the violence on foreign-backed terrorists and bandits and has ordered his troops to shoot to kill.

'Counter terrorism operation'

The presence of CTSO forces meant that Kazakhstani police could be redeployed to Almaty to take part in a "counter-terrorist operation", the president's office said.

The arrest of Massimov suggests Mr Tokayev is taking action against those deemed responsible for what he described as his country having "slept through" the preparations for attacks on Almaty, and elsewhere.

Besides heading the intelligence agency that replaced the Soviet-era KGB, Massimov was prime minister twice and worked closely with former president Nursultan Nazarbayev, who ruled for three decades until he handed the presidency to Mr Tokayev in 2019.

Mr Nazarbayev, who had retained significant power, was removed as head of the State Security Council on Wednesday, in a move some say may have been to mollify protesters who were shouting "Old man out!".

Occasional gunshots heard

In Almaty on Saturday, some businesses and petrol stations reopened and police and other security personnel patrolled the streets, although occasional gunshots could still be heard.

Meanwhile, police dispersed a demonstration and made arrests in the city of Aktau and sporadic gunfire was heard in Kyzylorda, the Russian agency Sputnik reported.

Mr Tokayev announced a national day of mourning to commemorate those killed in the unrest would take place on Monday.

The presence of Russia-led CSTO military forces in Kazakhstan at the invitation of Mr Tokayev comes at a time of high tension in East-West relations as Russia and the United States prepare for talks on the Ukraine crisis next week.