Tsvangirai, who is also president of the Movement for Democratic Change party, made his comments Thursday, the same day government authorities showed up to arrest Elton Mangoma, the country's minister of energy and power development, The New York Times reported.
Tsvangirai said the corruption charges against Mangoma were politically motivated.
"The fact of the matter is that Zimbabwe is in a crisis," Tsvangirai said Thursday.
Mangoma and the MDC have long been at odds with President Robert Mugabe, with whom Tsvangirai shares governing powers.
Mangoma and Tsvangirai were both reportedly beaten by police in 2007 for their efforts to unseat Mugabe.
"If South Africa, the African Union and the international community fold their arms, then Zimbabwe can descend into chaos," Mangoma said.
Tsvangirai said Mugabe's party, ZANU-PF, has launched a campaign to "promote chaos and fear in the country."
He cited the interruption by police of more than 70 MDC meetings in recent weeks, the harassment of opposition party members and an onslaught of negative reports about himself and supporters in state-controlled media.
Tsvangirai won more votes than Mugabe in a March 2008 general election, but he withdrew before a June runoff after widespread attacks on his supporters.
"ZANU-PF cadres and securocrats who murdered people in the run-up to the 27 June election are roaming free," Tsvangirai said.
He said Mangoma and six other activists were accused of treason after watching videos of uprisings in Egypt and Tunisia.
They were "innocent victims of barbaric and senseless dictatorship," Tsvangirai said.
Mugabe's supporters say activists are trying to overthrow him.
In a recent letter to the state-controlled newspaper Sunday Mail, Mugabe supporter Jonathan Moyo said "no doubt vigilance has become the order of the day all around."