Authorities said the six fishermen were killed by suspected armed young men from Warrap state.
"We have confirmed that the attackers are youth who came all the way from Luanjang community of Tonj East County of Warrap state," Kerjok said, calling the incident unfortunate.
Warrap state Minister of Information Wuol Mayom, told VOA fighting over fishing grounds are common in the area, adding fishermen from other South Sudanese states frequent the fishing pounds in Lakes state.
Mayom disputed that the alleged perpetrators were from the Luanjang area, challenging initial investigations.
He said there is continued crisis over fishing areas in the communities between Rumbek North and Luanjang.
Kerjok said Warrap and Lakes states officials plan to engage the two communities of Tonj East and Rumbek North counties in a dialogue aimed at reconciliations to avoid future clashes.
A peace conference aimed at restoring harmony between the two communities is set for early June.