Opposition leader Juan Guaidó was met with protests at the airport after returning to Venezuela from an international support-building tour.
Supporters of President Nicolás Maduro shouted "fascist!", grabbed Mr Guaidó's shirt and pushed him in the airport just outside the capital Caracas.
Mr Guaidó, 36, defied a travel ban to go to Colombia, Europe, Canada and the US, and met US President Donald Trump.
He is considered the legitimate leader of Venezuela by more than 50 countries.
However President Maduro, the country's left-wing leader who enjoys the support of the Venezuelan military, has remained in power.
One of the protesters, who shouted at Mr Guaidó and threw a liquid at him, was wearing the uniform of the state-owned airline Conviasa, which has been directly hit by US sanctions.
There were also scuffles between the protesters and supporters of Mr Guaidó, who had gone to the airport to welcome him.
Lawmakers loyal to Mr Guaidó had to walk to the airport after the bus they were travelling in was stopped by police.
Journalists reported being attacked and having their kit stolen by those who had turned out to boo Mr Guaidó.
Mr Guaidó's office later said that a relative who was travelling with him had been held by airport officials, and had not been seen since.