At least five people were killed and 16 wounded by the air strikes, local hospital sources said on Friday.
Warplanes began bombing purported hideouts of alleged al-Qaida operative Abu Musab al-Zarqawi at around 1pm (1000 GMT) on Thursday as talks between Falluja leaders and the Iraqi interim government collapsed.
US warplanes also struck the city in a pre-dawn raid on Friday morning.
"Since approximately 1pm (1000 GMT) Thursday, multinational forces have destroyed a key planning centre, a weapons transload and storage facility, two safe-houses, a terrorist meeting site and several illegal checkpoints used by the al-Zarqawi network," the US military said in a statement.
The US military increased its air raids on the city as a new offensive upsetting the months-long stalemate seemed to be imminent.
"Iraqis and elements of the First Marine Expeditionary Force increased security operations in and near Falluja tonight in order to disrupt preparations for terrorist attacks by anti-Iraqi forces. The status quo in certain cities in Iraq is unacceptable. This operation puts the anti-Iraqi forces in Falluja on notice."
The US military says al-Zarqawi
is hiding in the embattled city
Residents reported hearing loud explosions late on Thursday evening and the US marines said a round of raids were also carried out between 5.30pm (1430 GMT) and 8.30pm (1730 GMT).
"Several illegal checkpoints and a weapons cache were destroyed earlier this evening during the most recent strikes today against the terrorist network," the military said.
As the strikes multiplied, a delegation of city elders and leaders pulled out of talks with the Iraqi interim government, protesting against threats by the interim prime minister, Iyad Allawi, that the city would be invaded if it did not hand over al-Zarqawi and his supporters.
"We were taken aback by Allawi's comments since there was no mention of Zarqawi during the talks," one delegate, who gave his name as Abu Ahmad, said.
"Allawi and his government will bear the responsibility of the spilling of Muslim blood in Falluja."
He said delegates were close to reaching a breakthrough in talks that would allow Iraqi forces to come back into the city before Allawi imposed "impossible conditions".
"Allawi and his government will bear the responsibility of the spilling of Muslim blood in Falluja"
A Falluja delegate
"Basically he was telling us that he did not want to negotiate, so we suspended the talks from our end," he said.
Allawi on Wednesday demanded that Falluja turn over al-Zarqawi or face a military invasion as he sought to recover the city from the grip of fighters ahead of national elections in January.
In Baghdad, the government's national security adviser, Qasim Dawud, said he hoped the delegates could mediate a truce and rid the city of foreign fighters to avert a military showdown.
"I hope they kick them out, otherwise we are preparing to crush them," he said on Thursday evening.
Some residents say the dead and
wounded are mostly civilian
Dawud's comments came against a backdrop of US air strikes on the city on Thursday. Doctors and residents said at least three people were killed and eight wounded, while two houses, one of which was empty, were destroyed.
One strike in the al-Jubail area on the south-west side of Falluja destroyed the home of Haraj Rashid, his relative Amir Hamid said, adding that there were injured people under the rubble.
The US military carries out almost daily air raids on Falluja, insisting they are "precision strikes". Doctors and residents in the town say the dead and wounded are often ordinary civilians and include women and children.
US forces mounted a major operation in April to take the town but the assault ended in a stand-off, with Falluja transformed into a virtual no-go zone for US soldiers.