"They are using heavy, heavy guns. The army is retaliating with artillery."
The army said that the barrage had killed one soldier and injured two others.
Rajapakse said a convoy of 60 lorries, carrying around 600 tonnes of food aid for around 30,000 people displaced by war, had to turn back because of separatist artillery fire.
Direct talks offer
Reacting to the Tiger leader's speech, Mahinda Rajapakse, the Sri Lankan president currently visiting India, said he was ready to have direct talks with Prabhakaran.
| Velupillai Prabhakaran, the Tamil Tiger leader, said fighting would continue |
"I always tell him why do you need others to get involved in this - let us talk," Rajapakse said in an interview with India's New Delhi television.
Prabhakaran had accused the Colombo government of waging war against Sri Lanka's 2.5 million-strong Tamil minority under the cover of a 2002 peace agreement.
Asked if Sri Lanka was at war at present, the government's defence spokesman Keheliya Rambukwella said that Sri Lanka was committed to peace.
"We are pursuing peace ... But we will respond if we are attacked," he said. "We want a clarification from the Norwegians if the peace process is still on."
The demand was put in writing to Oslo - which brokered the ceasefire agreement in 2002 - along with a letter to the Scandinavia mission that is monitoring the truce, asking if the 2002 ceasefire remained in effect, said Rambukwella.
Truce monitors met senior Tiger members in the unofficial separatist capital, Kilinochchi, in the north on Tuesday morning, the group announced.
No further details of the meetings have been disclosed.