The ceasefire would take effect at 6 am on September 17 and would be in force till 6 pm on September 23, he told reporters here.
The measure has been taken as some Naxalites have sent a message that they desire to surrender and the government is giving them an opportunity do so, Shettar said.
Naxals are active in Western Ghat forests, particulary in Dakshina Kannada and Chikmagalur districts, officials said.
Shettar did not say how many Naxalites would surrender but added that key operatives had expressed a desire to lay down arms.
Karnataka already has a surrender policy for Naxalites.
The Chief Minister said the government is willing to give protection to surrendered Naxalites, encourage them to return to the mainstream and lead a normal life.
Defending the ceasefire decision, he said "we have not forced them. They have come forward. We have to encourage them (to surrender)".
The government would give them a package within the legal framework and as per the surrender policy.
Asked if criminal cases against them would be withdrawn, Shettar said it depends, noting that in case there are murder charges, the state can't interfere.
