The Swiss foreign ministry has said it is "extremely concerned" about the flare-up of hostilities in Sri Lanka.
On Monday it called on the parties to the conflict to halt the fighting immediately and go back to the negotiating table. The ministry said it was willing to assist in peace talks.
The foreign ministry's comments come after a day of heightened violence in Sri Lanka.
Tamil Tiger (LTTE) rebels have accused government forces of bombing an orphanage in the northeast of the country, killing at least 61 schoolgirls and injuring 155 other children.
The Sri Lankan government has denied the claim, saying the air force had targeted an LTTE training camp.
Hours later, a bomb explosion in the capital Colombo killed seven people and injured 17 others. The Tamil Tigers have denied responsibility.
"Switzerland regrets the immense suffering caused to the civilian population in the disputed territories," said the Swiss foreign ministry in a statement.
"It calls on the parties to the conflict to respect international humanitarian law and to protect the civilian population."
The statement described the alleged bombing raids on a children's home in northeast Sri Lanka "an outrage".
The ministry called for the two sides to restart peace negotiations and said it was willing to assist in carrying out talks as it did in Geneva in February this year.
On this occasion Switzerland hosted the Norwegian-organised talks between the Tamil Tigers - who want a separate homeland in the north and east of the country - and the Sri Lankan government.
The meeting ended with the Sri Lankan government and the Tamil Tigers agreeing to respect the 2002 ceasefire between the two sides and to stop all forms of violence. But tensions have been increasing since April.
The latest chapter of violence has centred on a Tamil stronghold in the northeast and started after rebels cut off water supplies from a reservoir.
Swiss aid agencies in Sri Lanka expressed concern last week following the shooting of 17 workers from a French relief organisation in the area on August 7.
The Swiss foreign ministry has also condemned the assassination in Colombo on Saturday of Ketheesh Loganathan, the deputy secretary general of the Sri Lankan government's peace secretariat.
It said Loganathan, who had coordinated the government's side of the Norway-brokered peace process, had made "a decisive contribution to the search for a peaceful solution to the conflict".
swissinfo with agencies
The conflict in Sri Lanka has cost an estimated 62,000 lives, with some 800,000 people displaced in the past 20 years.
Switzerland donated SFr10.5 million ($8.6 million) of emergency aid to Sri Lanka following the 2004 tsunami – raising the total aid payments to the country to SFr16.95 million in 2005.
More than 35,000 Sri Lankans, mostly Tamils, live in Switzerland, of which ten per cent are naturalised Swiss. The expatriate community is now one of the largest after those in Canada, Germany and Britain.