Hundreds of Lebanese journalists gathered in a sit-in at the parking lot of Future TV in Beirut to protest against the assault against its reporter, the broadcaster aired Friday.
Omar Harqous, who works as a reporter for Future TV owned by majority leader Saad Hariri, was badly beaten, with wounds in the head, neck and chest by members of the Syrian Socialist National Party (SSNP), the report said.
The army has arrested five members of the Lebanese opposition party, who were involved in the assault in Hamra area of west Beirut on Thursday.
Harqous was attacked when covering attempts by Beirut municipality employees to remove a SSNP poster, in line with an agreement reached between the Western-backed majority and the opposition over a month ago to defuse tension by removing all political posters.
The SSNP set the Future TV building on fire in riots between the opposition and the government supporters in early May, leading to the Arab intervention and the production of a Qatari-brokered accord between rival Lebanese groups in Doha on May 21.