Anti-Gaddafi fighters bombarded loyalist positions in the deposed leader’s home town of Sirte on Tuesday.
Heavy shelling was launched from the outskirts.
One fighter blamed Gaddafi supporters for the failure to establish a temporary ceasefire.
“Today, Gaddafi started attacking the same area again to make it impossible for the ceasefire or maybe he is thinking that we are still in this area,” he said.
In Tripoli, forces allied to the interim leadership stormed a house on Tuesday. There were chaotic scenes, as they confiscated weapons and detained four brothers, who they say were planning attacks in the capital in support of Muammar Gaddafi.
Meanwhile, in New York, Libya’s new flag flew for the first time at UN headquarters.
“The Libyans are so pleased with this day when the flag of Libyan independence flew at the United Nations, reflecting the wishes of the former rebels and the Libyans,” said Mustafa Abdul Jalil, head of Libya’s National Transitional Council.
Libya has reverted to the national flag that was used from 1951 until Gaddafi introduced a green one, 26 years later.
In an audio statement, Gaddafi himself has declared his regime cannot be toppled. He warned that his fightback will begin when NATO ends its mission in Libya.