KIEV, Dec. 21 – The Prosecutor General’s Office will address Parliament on Wednesday on the progress it has made on the investigation of a recent attack by pro-government lawmakers that left four opposition lawmakers hospitalized.

A request for the address was approved by 300 lawmakers in the 450-seat Parliament, bowing to pressure from opposition groups.

The development comes after the largest opposition group, Batkivshchyna, threatened to boycott sessions of Parliament until the attack is properly investigated and those responsible punished.

The Kiev Prosecutor’s Office on Tuesday opened the investigation into the attack that left four opposition lawmakers, some with serious injuries, hospitalized on Thursday.

“We have to urgently ask the leadership of the prosecutor general’s office to come to Parliament and to report on the progress of the investigation,” Batkivshchyna said in a statement.

The four opposition lawmakers, some with serious injuries and bleeding, were rushed to the hospital late Thursday after allies of President Viktor Yanukovych ferociously attacked the group for blocking podium in Parliament.

The group of about 30 opposition lawmakers blocked the podium in protest of what they call the politically motivated persecution of former Prime Minister Yulia Tymoshenko.