Venezuela-Argentina spat over human rights comments
Venezuela has accused the new Argentine President Mauricio Macri of meddling in its internal affairs after he criticised its human rights record.
Venezuelan Foreign Minister Delcy Rodriguez hit back after Mr Macri made his remarks at a meeting of regional leaders in Paraguay.
The two countries had previously been allies for more than a decade.
The UN, the European Union and the US have also put pressure on Venezuela to release jailed opposition leaders.
Speaking at the summit of the regional Mercosur bloc, Mr Macri called on all South American leaders to push for the release of Venezuelan political leaders.
"There can be no place for ideological persecution in Mercosur member states," Mr Macri said.
The Venezuelan government has denied holding political prisoners, but the jailing of several high-profile opposition leaders like former mayors Leopoldo Lopez and Antonio Ledezma has drawn condemnation from human rights groups, the UN, the EU and the United States.
Leopoldo Lopez was sentenced to nearly 14 years in jail in September on charges of inciting violence during anti-government protests last year in which 43 people died.
In response to Argentina, the Venezuelan Foreign minister, Delcy Rodriguez, accused Argentina of not bringing to justice some of those who had committed human rights abuses during the military government of the 70s and 80s in Argentina.
Venezuelan President Nicolas Maduro did not attend the Mercosur summit.
Before taking office on 10 December, Mr Macri had called for Venezuela to be kicked out of Mercosur for violating its "democracy clause".
But he changed his stance after Venezuela's opposition won a landslide victory in legislative elections on 6 December.