Manuel Rosales, an exiled Venezuelan opposition politician, has been arrested upon his return from self-exile, six years after the government of late socialist leader Hugo Chavez charged him with corruption in 2009.
He was expected to appear in a Caracas court later on Friday.
Rosales, who served two terms as governor of the most populous state of Zulia, joins a list of opposition figures - including protest leader Leopoldo Lopez - who have been jailed by the government of President Nicolas Maduro.
Hundreds of supporters gathered at a rally on Thursday to support him while the intelligence agents took Rosales into custody after he landed in Zulia's capital Maracaibo.
Upon landing in Venezuela, Rosales made a statement over returning home.
"Hello to all the people on [street] 72 from the airport, the streets of Maracaibo, from Zulia, from all of Venezuela who are waiting for me with love, passion in search of the better horizon of a better future for Venezuela. I feel so excited that my heart is skipping a beat," he said.
Rosales' arrival and detention may help mobilise the opposition in the run-up to the December 6 parliamentary elections, which opinion polls show will be among the toughest ever for the ruling Socialist Party and a test for Maduro.
The attorney general's office warned Rosales that he would be detained on charges of stealing public money when he announced his plans last Friday to return home.
His lawyer, Jesus Ollarves, said Rosales had expected to be arrested but returned anyway at the request of his family and political party, and because he came to believe that "exile is the worst prison".
Polls say the opposition is on track to win the December elections, potentially dealing the first decisive ballot-box defeat to the socialist party in 16 years.