Tripoli, Libya (CNN) -- Coalition forces hit Libya for a sixth day early Thursday amid questions over the future of the international involvement in the effort to halt civilian attacks by the nation's forces.
So far, the coalition has crippled the Libyan air force and established a no-fly zone along the nation's coastline, U.S. Navy Rear Adm. Gerard Hueber said.
Allied forces gave no indication that ruler Moammar Gadhafi was complying with a United Nations mandate to stop attacks against civilians.
But a U.S. official said though the rebels are in a better position, the ruler's forces still have the upper edge.
They remain capable of carrying out attacks on the opposition, are relatively well-organized and continue to fight effectively, the official said.
Meanwhile, explosions could be heard in an area east of Tripoli early Thursday.
Regime forces also attacked the city of Misrata on Wednesday night as residents implored the international community to help.
Gadhafi's forces attacked the city's main hospital, where 400 people -- about half of them patients -- were at the time, a witness said.
At one point, shelling occurred without respite for 40 minutes, he said.
"Now, fortunately, no more shelling, but the situation is so serious that all the teams here -- the doctors, the patients -- are paralyzed, scared."
He called for international intervention to protect the civilians inside the institution.
Nobody can work because ambulances cannot leave the hospital, which has lost its electricity and is using generator power, he said.
As attacks rage on, some critics are concerned about the future of the coalition.
U.S. President Barack Obama faces questions about who will take over command of the mission and what the exit strategy will be. NATO said Wednesday it will decide shortly what its role in the operation will be, adding that the alliance is well-prepared.
The timetable for a transition of military leadership will be coming in days, Obama said this week.
Critics are also calling for a clearer explanation of U.S. policy in the North African nation.
Obama, who just wrapped up a five-day trip to Latin America, has insisted that the goal of the U.N.-sanctioned military mission is strictly to prevent a humanitarian crisis.
Specifically, the U.N. mandate calls for protecting Libyan rebels and other civilians from attacks by forces loyal to the strongman.
U.S. officials have indicated they hope the dictator will be removed quickly by forces currently loyal to him, though they haven't publicly called for a coup.
Critics said there was inadequate administration consultation with the Congress before the start of the military mission over the weekend. They are also questions over the conflict's cost and consequences, as well as the U.S. endgame.
Mission officials said they are ensuring no civilian are affected by the strikes.
Coalition jets are using smart bombs to target mechanized forces like Libya's premier 32nd Brigade, Hueber said. The brigade is commanded by one of Gadhafi's sons and is fully engaged in the fighting.
"It's an extremely complex and difficult environment," Hueber said about going after forces in populated areas.
"And our primary focus is to interdict those forces before they enter the city ... cut off their lines of communication and cut off their command and control," he said.
The international airstrikes against Libyan military positions began over the weekend after Gadhafi defied a United Nations-mandated cease-fire to stop attacks against civilians.
The war was sparked in February by protests demanding an end to Gadhafi's nearly 42-year rule. The Libyan strongman responded with force against civilians, prompting the international community to take action.
France launched the air campaign, and Britain and the United States followed.
Germany is not participating in the military action, though it agrees with the United Nations resolution in principle, and moved Wednesday to ensure that its ships were far removed from the fighting.
Britain has announced an international meeting for next Tuesday to assess the situation in Libya.