A brutal crackdown in Zimbabwe that has followed protests against fuel price rises is “just a foretaste of things to come”, the president’s spokesman has said.

The harsh words will increase concerns about the deteriorating human rights situation in the poor southern African country, coming after a week in which police and soldiers have beaten civilians, shot 12 people dead and detained at least 600 people, many without charge.

“[The] government will not stand by while such narrow interests play out so violently,” President Emmerson Mnangagwa’s spokesman George Charamba told the state-controlled Sunday Mail newspaper.

The repression followed a national strike called by unions after the government ordered a massive fuel price hike eight days ago.

The price rise, of about 250%, is the latest blow to millions of citizens who are increasingly unable to buy basics such as fuel, food and medicines.

Inflation is running at 40% – its highest rate since hyperinflation forced Zimbabwe to abandon its currency 10 years ago in favour of dollars, electronic cash and “bond notes” issued by the central bank.

The violence is the worst seen in Zimbabwe for a decade, prompting many to make comparisons with the worst days of the 37-year rule of the autocratic former president Robert Mugabe.

The government has called the unrest “terrorism” and blamed the opposition party, the Movement for Democratic Change (MDC).

Mnangagwa, a ruling Zanu-PF party stalwart, took power when Mugabe was ousted in a military takeover in November 2017 and then won contested elections last year.

On Sunday the president, who has been touring central Asia, Russia and Europe in a bid to drum up investment for the country’s crippled economy, said he would return to Zimbabwe instead of attending this week’s World Economic Forum in Davos.

“In light of the economic situation, I will be returning home … The first priority is to get Zimbabwe calm, stable and working again,” Mnangagwa tweeted.

The Zimbabwe Association of Doctors for Human Rights said it treated 68 gunshot wounds and 100-plus other cases of “assaults with sharp objects, booted feet, baton sticks” last week.

There were further reports of violence over the weekend, as army and police patrols searched hundreds of homes in Harare, the capital, for property stolen in outbreaks of looting last week.

Large numbers of people remain missing – including senior union officials involved in organising the three-day shutdown.

Armed police were also reported to have surrounded the homes of senior officials and parliamentarians from the MDC.

Chalton Hwende, the MDC representative for Kuwadzana East, a poor area on the outskirts of Harare, said six opposition lawmakers were already in custody. Some have been charged with inciting violence, though the party was careful to call for peaceful protests and was not involved in the organisation of the shutdown.

“This is all just an excuse to destroy the MDC. Mugabe was just the face of the machine. We always expected things to get worse,” Hwende said.

A family member reacts during the funeral of Kelvin Tinashe Choto, who was shot dead in Chitungwiza. Photograph: Tsvangirayi Mukwazhi/AP

Much of the repression has been concentrated in poor neighbourhoods and satellite towns of Harare, such as Chitungwiza and Ruwa, which voted heavily for the MDC in the elections last July.

On Saturday, a series of funerals brought hundreds on to the streets. Neighbours of a 35-year-old shot on the second day of the crackdown described “unidentified [people] monitoring the dead man’s family”.

Kelvin Tinashe Choto, 22, was shot in the head while watching the protests in Harare.

“He was our future,” said his father, Julius Choto, as the family buried him in Chitungwiza on Saturday. “I have been robbed. He was my only son and his future was bright. I have been robbed by the state.”

The end of Mugabe’s rule prompted widespread optimism that the repression of previous decades was over.

But any faint hopes of political reform have been extinguished. The crisis has attracted fierce criticism from western powers, and will undermine Zimbabwe’s efforts to rejoin the international community after decades as a pariah.

Mugabe’s rule left Zimbabwe with vast debts, a crumbling infrastructure and soaring unemployment, especially among young people. Most of its 16 million people live hand-to-mouth, or survive on remittances from the extensive diaspora.

Albert Taurai, in hospital in Harare with a broken spine, said he had gone to buy food when he was attacked by a group of armed men in plain clothes.

They struck him with iron bars on the back, thighs and ankles, saying “Zimbabwe will never be shut down”.

“I have seen both Mugabe and Mnangagwa. This just is worse than Mugabe,” Taurai, 46, said.