The attacks came just before Lieutenant-General Rupert Smith arrived in Sarajevo to assume command of UN peace-keepers in Bosnia, which has been relatively quiet since the signing on New Year's Eve of a deal to halt hostilities.
"Six shells were reported impacting within the town of Bihac, within the `safe area', with UN military observers confirming an injury to one civilian," a UN spokesman said in Zagreb.
"The shells are believed to have come from Bosnian Serb army positions ... an additional number of shells were fired from what are believed to be [Croatian Serb] positions towards Coralici."
Ground fighting continued north of the Bihac pocket between the Bosnian army and rebel Muslims, loyal to a local businessman, Fikret Abdic.
"We remain very concerned about the level of fighting in that area," the UN spokesman said. More than 300 explosions had been recorded on the frontline near the town of Velika Kladusa, where Mr Abdic's forces are attempting to push back the Sarajevo government's troops.
The Bihac pocket is the hottest spot facing General Smith, who took over from Lieutenant-General Sir Michael Rose on Tuesday. General Smith said he hoped to build a lasting peace on the shaky truce brokered by his predecessor.
On being asked whether General Rose had offered any advice, he said: "`Good luck' were his parting words."