A Texas businessman has filed a lawsuit in a bid to stop the state's governor from placing huge buoys in the Rio Grande to block migrants trying to cross the river, the man's lawyer said Saturday.

"New marine barrier installation on the Rio Grande begins today," Governor Greg Abbott, a Republican, said Friday on Twitter, in a post that included video of workers unloading huge orange buoys from flat-bed trucks.

It was not clear Saturday whether installation of the buoys had actually begun.

Abbott regularly accuses US President Joe Biden of allowing thousands of undocumented migrants to enter the country. He has vowed to block the flow.

But businessman Jessie Fuentes, owner of Epi's Canoe and Kayak Team, said Abbott's plan would place a "wall" of buoys in the exact location near Eagle Pass where his firm offers river tours. Fuentes is suing the state and Texas officials to stop the operation.

"The governor and the defendants do not have the legal authority under Texas law or federal law to install those buoys," Carlos Flores, Fuentes's lawyer, told AFP.

The lawsuit further asserts that emplacement of the buoys would require federal approvals that, as of Friday, Abbott had yet to receive.

The buoy installation is part of a "Lone Star" operation the state is pursuing to secure its borders, but activists and some legislators say Abbott is exceeding his authority.

The governor has insisted he has the right to act and expects to be vindicated even if the case reaches the US Supreme Court.

Previously, during the Covid-19 pandemic, US authorities invoked a law known as Title 42 to swiftly expel an array of migrants on public health grounds -- usually without sanctions -- but that authority ceased on May 11 when the government declared an end to the health emergency.

Since then, a law known as Title 8 has prevailed, providing for strict penalties for those crossing who do not qualify for asylum, including five-year bans on entering the country and possible criminal charges.

The change has led to a "significant reduction" in the number of migrants reaching the southwest US border, federal officials said in mid-June.