BEIRUT, March 24 (Reuters) - A Lebanese judge on Thursday instructed customs authorities to prevent six banks from moving money out of Lebanon, according to a copy of the decision seen by Reuters, taking further steps against lenders whose assets she has already ordered frozen.

A lawyer for the Lebanese banking association urged the public prosecutor to halt implementation of the decision by Judge Ghada Aoun, saying the law did not give her the power to limit the freedom to ship money and the move would add to the deterioration of the Lebanese pound's value against the dollar.

Thursday's decision applies to Bank Audi, Bank of Beirut, Creditbank, SGBL, Blom Bank and Bankmed.

Banks staged a two-day strike this week in protest against what they called arbitrary judicial decisions.

Raya Hassan, chairman of the board of Bankmed, said the decision would lead to Lebanese banks being isolated from banks abroad, speaking in an interview with broadcaster MTV.

Earlier this month, Aoun froze the assets of Bank Audi, Bank of Beirut, Blom Bank, Bankmed and SGBL and members of their boards while she investigates transactions the banks undertook with the central bank.

She also banned the heads of their boards from travel.

In a separate action, Aoun issued a travel ban for the chairman of Creditbank and froze all the banks assets.

She has not charged any of the parties mentioned with any crime.

In an open letter to the public prosector, Akram Azoury, the lawyer for the Association of Banks in Lebanon, said the measure "touches the core of banking work" and would destroy "what is left of confidence in the banking sector".

Lebanon has been mired in one of the world's sharpest ever financial meltdowns since 2019, when the economy collapsed under the weight of a huge public debt caused by decades of state corruption and waste, and the unsustainable way it was financed.

Depositors have been largely frozen out of hard currency accounts since then, and the Lebanese currency has lost more than 90% of its value.

Aoun's latest decision was based a legal complaint filed by an activist group "the people want to reform the system" which said the move was to prevent deposits being moved out of the country.

(Reporting by Laila Bassam; Writing by Tom Perry; Editing by Kirsten Donovan)