Tripoli, Libya (CNN) -- Libyan forces pounded parts of Misrata on Tuesday, with tanks firing mortar shells and troops using heavy artillery in an effort to retake control of the city, a witness told CNN.
Coalition planes circled overhead but did not strike the tanks, he said.
As representatives of numerous countries met in London to decide the next steps in the Libya effort, Libyan leader Moammar Gadhafi showed no sign of letting up his effort to crush the rebellion that seeks an end to his nearly 42 years in power.
The day after Gadhafi's regime tried to convince journalists that it was in control of Misrata by taking them on a trip to part of the city but not allowing them into the city center, his troops were killing and wounding civilians and evicting thousands of people from their homes, the witness told CNN.
"The carnage and the destruction and the human suffering from both the evictions and... terrorizing the city -- it's beyond imagination," said the witness, an opposition councilman in Misrata, in western Libya east of Tripoli. "It's incredible."
Gadhafi forces did not even allow people to take belongings with them from their homes, he added. "They tell them, 'Run for your lives,' and fire bullets just above them."
Troops are looting the homes, he said.
CNN could not independently verify the witness' descriptions.
Meanwhile, rebels in Bin Jawad battled Gadhafi forces and came under a hail of artillery and rocket attacks, an opposition source said.
CNN saw rebel fighters streaming back out of the city. One said the barrage was too much for the opposition to withstand, and that Gadhafi loyalists had infiltrated the city.
A man in car that drove by a CNN crew in the area shouted, "Gadhafi will be back."
The violence came the day after U.S. President Barack Obama delivered an address explaining his decision to commit U.S. forces to the U.N.-authorized military mission in Libya.
"To brush aside America's responsibility as a leader and -- more profoundly -- our responsibilities to our fellow human beings under such circumstances would have been a betrayal of who we are," Obama said. "Some nations may be able to turn a blind eye to atrocities in other countries. The United States of America is different. And as president, I refused to wait for the images of slaughter and mass graves before taking action."
The president cited what could have been a massacre in Benghazi, which has become an opposition stronghold in Libya.
The witness in Misrata on Tuesday, in an interview with CNN, pleaded for coalition forces to strike Gadhafi's forces in that city.
"We call on the international community, especially the American forces and the American people, to please save Misrata from a massacre," he implored.
Gadhafi's forces were "advancing in all directions of the city," the witness said.
Battles have been under way in Misrata for weeks.
Off the coast of Misrata, U.S. military planes fired at three Libyan boats, destroying one and damaging the other two, military officials said in a statement Tuesday. The Libyan ships were targeted because of reports that they were firing indiscriminately at merchant vessels in the port of Misrata on Monday, the statement said.
Libyan state TV had a banner Tuesday saying, "Civilian and military locations in Misrata, Tripoli, Zaltin, Mazda and al-Watiya are being bombed by the crusaders and colonial enemies."
The central group representing the opposition and working to plan a new government if Gadhafi were to fall issued a statement Tuesday describing its "vision of a democratic Libya."
"We have learned from the struggles of our past during the dark days of dictatorship that there is no alternative to building a free and democratic society and ensuring the supremacy of international humanitarian law and human rights declarations," the statement from the Interim National Council said.
The group representing numerous areas throughout Libya has been meeting in Benghazi
In the statement, the council vowed to draft a constitution, guarantee key rights to every Libyan citizen, respect freedom of expression, and establish "a state that draws strength from our strong religious beliefs in peace, truth, justice, and equality."
Much of the statement focused on promises to build a better economy that would eradicate poverty.
The CIA World Factbook says about a third of Libyans live at or below the national poverty line.
The council issued its statement in coordination with the meeting in London.
U.S. Secretary of State Hillary Clinton met with a leader of the council Tuesday at meeting, part of a U.S. effort to expand ties with rebel leaders fighting to oust Gadhafi.
It was the second meeting in less than two weeks between Clinton and the Libyan Interim National Council's Mahmoud Jabril, a former head of Libya's economic planning council.
The United States will also send a liaison to the eastern Libyan city of Benghazi to open up a more direct line of communication with members of the opposition, a senior administration official told reporters Tuesday. The official did not say when.
The U.S. government has spent about $550 million on the Libya effort, the Pentagon said Tuesday, adding that about 60% of that went to munitions. Another $40 million is expected to be spent over the next three weeks. Then, costs are expected to be about $40 million per month, said Pentagon spokeswoman Cmdr. Kathleen Kesler.
More than 40 foreign ministers and representatives from regional groups attended the conference Tuesday in London, including U.N. Secretary-General Ban Ki-moon and Chairman of the African Union Jean Ping.
"The purpose of this conference is to broaden and deepen the coalition effort," said British Foreign Secretary William Hague. "We all want to see that cease-fire. We all want to see Gadhafi go. Those things are clear. But once we have that cease-fire, we have something to work with."
Opposition fighters have credited coalition airstrikes with helping them advance in their rebellion.
Organizers of the conference said it will look for ways to strengthen the U.N. Security Council resolution approved on March 17 that created a no-fly zone above Libya and mandated the protection of civilians. They will also search for urgent ways to get humanitarian aid to war-torn cities like Misrata.
NATO plans to take full control of the Libya mission by the end of the week.
"Our mandate is very clear. We're there to protect civilians against attacks. No more, no less," NATO Secretary-General Anders Fogh Rasmussen told CNN.
CNN's Reza Sayah, Arwa Damon, Nic Robertson, Paula Newton, Maxim Tkachenko and Yousuf Basil contributed to this report