Keheliya Rambukwella, a government spokesman, said Sri Lankan war planes struck a Tamil Tiger base on Friday, the third day of bombing.
Rambukwella said: "The airforce carried out another round of aerial attacks against the Tigers today in the Trincomalee area."
He said the bombing campaign was aimed at opening an irrigation canal shut down by the Tigers that he said had deprived a large farming community in the area of water.
Rambukwella said that members of the Swedish-led Sri Lanka monitoring mission had gone to the area in a bid to settle the water issue.
Finland became the first country to announce a withdrawal after the rebels demanded EU member states stop monitoring a Norwegian-arranged ceasefire in place since 2002.
The announcement was swiftly followed by a similar statement from Denmark, which described the pull-out of its 12 monitors as "most regrettable".
The Danish foreign ministry said: "The withdrawal will be completed before September 1 2006."
The Tamil Tigers demanded that observers from the three countries leave the island after the EU added the group to its list of "terrorist" organisations in May.
This would leave only Norwegian and Icelandic monitors on the island.
Diplomats said Norway is to send Jon Hansse-Bauer, a special envoy, to Sri Lanka next month to try to salvage the ceasefire.