Sri Lankan judges and lawyers boycotted courts on Monday to protest an assault on an outspoken judge, and hundreds of lawyers staged a demonstration demanding a thorough investigation into the attack.

About 500 lawyers and staff wearing black headbands marched in front of Colombo's court complex. They carried a coffin, saying the weekend attack on Judge Manjula Tilakaratne represented the death of an independent judiciary. Later, they burned the coffin.

They held placards reading: "Stand up to protect the judiciary. Protect lives of judges. Arrest those who attacked a judge."

Tilakaratne, secretary of the Judicial Service Commission that handles appointments and transfer of judges, was attacked by four men on Sunday as he was in his car reading a newspaper after dropping off his son at school. He sustained injuries to his face and right hand. Police said an investigation is under way.

Protesters said Tilakarartne had irked the government with a statement two weeks ago complaining of outside influences on the commission's decisions.

A protesting lawyer, J.C. Weliamuna, said the attack was "unprecedented" and blamed the government.

Another lawyer, Gunaratne Wanninayake, demanded that police conduct an impartial inquiry.

"This attack symbolizes the death of Sri Lanka's independent judiciary. It's not just an attack on one judge, it has dealt a severe blow to the whole judiciary," he said.

District judges stayed away from work Monday, while lawyers also boycotted courts across the country, said lawyer Nuwan Bopage.

In July, lawyers accused a government minister of threatening a judge. The politician's supporters were accused of stoning the court complex.