Gunmen stormed the offices of the Uthayan newspaper in Jaffna, 400 kilometres (250 miles) north of the capital Colombo, Tuesday night, killing a manager and another employee, journalists and officials said.
Six people were arrested in connection with the attack, a government spokesman announced at a ceremony to mark international press freedom day celebrations attended by President Mahinda Rajapakse.
"We have just been informed that six people have been arrested in connection with yesterday's attack," the spokesman said.
However, police said the six men were later freed after those who survived the attack failed to pick them out as being the gunmen involved in the storming of the newspaper offices.
The attack further added to the 200 people killed in the bloodiest month since a 2002 truce took effect between the rebels and government.
The government said the murders were timed to embarrass it as Sri Lanka hosted UNESCO World Press Freedom Day celebrations, while the rebel Tamil Tigers