SAN JUAN - The legitimacy of Puerto Rico's newly-installed governor has been challenged in court, the Wall Street Journal reported on Monday, adding further drama to who will lead the U.S. territory after weeks of protests.

Pedro Pierluisi, the handpicked successor to disgraced former governor Ricardo Rossello, was sworn in on Friday.

Pierluisi, 60, said his term might be short as the island's Senate still had to ratify his position.

That vote was expected to happen on Wednesday.

But late on Sunday, Puerto Rico Senate President Thomas Rivera Schatz sued Pierluisi in a San Juan court, claiming he usurped the office by ignoring a constitutional requirement for the Senate to vote to confirm him, the Journal reported.

Pierluisi, a lawyer who formerly advised the despised, federally-created board supervising Puerto Rico's bankruptcy, was sworn in even though his appointment had not yet gone before the Senate for a vote.

The lawsuit asks the court to strip him of the title and stop him performing any acts as governor, the Journal reported.

Reuters could not confirm the lawsuit, nor reach Pierluisi or Schatz for comment early on Monday.

At his first news conference as governor last week, Pierluisi acknowledged that Puerto Rico's Senate was still to meet to vote on whether to confirm his position.

Schatz has previously said that installing Pierluisi before the vote was "unethical and illegal."

But Pierluisi had countered: "The Senate will have its say and by the end of Wednesday we'll know whether I am ratified.".

If he is not ratified then the second in line, the secretary of justice of Puerto Rico, will take over the governorship, he said.

Rossello, a 40-year-old, first-term governor, had tapped Pierluisi as secretary of state, a position putting him first in line as successor. -Reuters