Zimbabwean President Emmerson Mnangagwa has broken off a trip to Europe amid violent protests in his home country.
Mnangagwa had been due to attend the Davos economic summit where he was expected to seek investment for Zimbabwe.
Ministers say the opposition Movement for Democratic Change (MDC) is using sharp fuel price increases as a pretext for violence.
But the MDC accuses the authorities of a brutal crackdown.
Mnangagwa's announcement of a steep increase in the fuel price over a week ago led to angry protests in the capital, Harare, and the south-western city of Bulawayo.
Rights groups say at least 12 people have been killed but this has not been officially confirmed.
Mnangagwa arrived back in Harare late on Monday night.
Earlier, MDC leader Nelson Chamisa said many of the party's members had been detained including four MPs.
He accused security forces of attacking families in their homes.
The Zimbabwe Congress of Trade Unions, the umbrella group that called the protests, says its leader Japhet Moyo has also been arrested.
As tensions rose, the government said on Sunday that the security forces' actions were just "a foretaste of things to come".
