The Lebanese Bar Association condemned the closure of Murr Television (MTV) as a curtailment of freedom and democracy.
The US Embassy in Beirut also denounced the move, saying it "called into question Lebanon's commitment to freedom of press".
State security forces closed MTV on Wednesday, after a court accused it of violating an election law against broadcasting political propaganda.
The strike brought legal proceedings to a halt throughout Lebanon.
About 150 court sessions had to be adjourned, a judicial source told the Associated Press news agency.
'Score-settling'
MTV is owned by businessman Gabriel Murr, a Christian lawmaker opposed to Syrian political influence its military presence in Lebanon.
The station was charged following its coverage of a fiercely contested by-election in June, which Mr Murr narrowly won.
MTV's lawyers have appealed against the closure, arguing that the station has not violated the law.
Critics of the closure say it was aimed at silencing criticism of the pro-Syrian government and Syria.
A US embassy statement said: "This unfortunate incident is at odds with Lebanon's long history of commitment to freedom of speech and political expression."
The Paris-based press watchdog, Reporters Without Borders, said the decision reeked of political score-settling with the Christian opposition.
The New York-based Committee to Protect Journalists said the closure was a threat to press freedom, and it called for the station to be allowed to reopen immediately.