The U.S. on Tuesday targeted six oil tankers in new Venezuela-related sanctions, escalating pressure on the government of President Nicolas Maduro.

The Treasury Department added five Venezuela-flagged and one Panama-flagged vessels linked to Venezuela’s state-owned oil company, PDVSA, to its sanctions list.

“Today’s action further targets the former Maduro regime’s corruption in the oil sector and the mechanisms used to transport oil to the Cuban regime in return for security and intelligence assistance,” said the department in a statement.

Treasury Deputy Secretary Justin Muzinich accused Cuba and Venezuela of circumventing sanctions by changing the vessels’ names and facilitating the

Read more: US puts 6 oil tankers on Venezuela sanctions list