By Maria Golovnina
TRIPOLI (Reuters) - Muammar Gaddafi's government said it was declaring a unilateral ceasefire in its offensive to crush Libya's revolt, as Western warplanes prepared to attack his forces.
But government troops pounded the rebel-held western city of Misrata on Friday, killing at least 25 people including children, a doctor there told Reuters. Residents said there was no sign of a ceasefire.
And in the rebel-controlled east, the government declaration was dismissed as a ruse or a sign Gaddafi was desperate.
"We have to be very cautious. He is now starting to be afraid, but on the ground the threat has not changed," a French spokesman said. Britain, like France a strong advocate of armed action, said it would judge Gaddafi by "actions, not his words".
The United States, whose role is crucial despite its insistence it is not leading the international campaign, was also skeptical. "We would have to see actions on the ground and that is not yet at all clear," Secretary of State Hillary Clinton said.
Turkey, an opponent of military action, said the Libyan ceasefire should go into effect immediately.
"We decided on an immediate ceasefire and on an immediate stop to all military operations," Libyan Foreign Minister Moussa Koussa said in Tripoli on Friday, after the U.N. Security Council passed a resolution authorizing military action.
He called for dialogue with all sides. Gaddafi had vowed to show "no mercy, no pity" on Thursday, and rebels pleaded for foreign aid before time ran out.
The ceasefire announcement was probably prompted by Gaddafi's realization that air strikes could seriously degrade his military, said John Drake, senior risk consultant at AKE.
"The Gaddafi regime may be willing to negotiate," he told Reuters. "With talk of strikes against military convoys he may be concerned about a significant attack on his military."
Officials said one or more Arab countries would play a role in the Libya operation. Gulf state Qatar said it would take part but it was unclear whether that meant military help. Tunisia said it would not play any role.
"Britain will deploy Tornadoes and Typhoons as well as air-to-air refueling and surveillance aircraft," Prime Minister David Cameron told parliament.
"Preparations to deploy these aircraft have already started and in the coming hours they will move to airbases from where they can start to take the necessary action."
Italy said it would make seven military bases available along with equipment and troops and Naples could be the coordination center.
Denmark and Canada said they planned to contribute warplanes. France is to host talks on Saturday to discuss the action with British, Arab League and other leaders.
NATO Secretary-General Anders Fogh Rasmussen said after a meeting of alliance ambassadors that NATO was "completing its planning in order to be ready to take appropriate action... as part of the broad international effort".
People in Misrata said the rebel-held western city was under heavy bombardment by Gaddafi's forces on Friday.
"They are bombing everything, houses, mosques and even ambulances," Gemal, a rebel spokesman, told Reuters by phone from the last big rebel stronghold in the west.
Another rebel named Saadoun said: "We believe they want to enter the city at any cost before the international community starts implementing the U.N. resolution.
"We call on the international community to do something before it's too late. They must act now."
A fighter named Mohammed said tanks were advancing on the city center. "All the people of Misrata are desperately trying to defend the city," he said.
Al Arabiya also said the rebel-held western town of Zintan was attacked by rockets on Friday. The fighting reports could not be independently confirmed. Authorities were preventing Tripoli-based foreign journalists from reporting freely.
REBELS SCORN CEASEFIRE
In rebel-controlled Tobruk in the east, there was scorn for the ceasefire call. On Thursday, Gaddafi had vowed "no mercy and no pity".
"See how things change from night to day," said Ashraf Afgair. "They are just trying to calm international opinion. It's a desperate attempt by Gaddafi to cling to power."
Idris Khamis said: "They have reached the end of the line. That's why they are accepting the U.N. decision. Otherwise it's the same fate for Gaddafi as Hitler and Mussolini."
But Gaddafi's troops did not fulfill his threat to overrun the rebel base of Benghazi overnight after their rapid counter-offensive brought them to within 100 km (60 miles) of the eastern city.
The U.N. Security Council passed a resolution endorsing a no-fly zone and "all necessary measures" to protect civilians from Gaddafi's forces.
Libya's military airfields are mostly strung along the Mediterranean coast, as are its population centers. Gaddafi's ground troops are advancing from the west along the main coast road toward Benghazi in the east.
While other countries or NATO may play roles in military action, U.S. officials expect the United States with its extensive air and sea forces to do the heavy lifting in a campaign likely to include air strikes on tanks and artillery.
Ten of the Council's 15 member states voted in favor of the resolution, while Russia, China and Germany were among five that abstained. The resolution was co-sponsored by France, Britain, Lebanon and the United States.
Apart from military action, it expands sanctions against Gaddafi and associates. Among firms whose assets it orders frozen are the Libyan National Oil Corp and the central bank.
Rebel National Council head Mustafa Abdel Jalil told Al Jazeera television air strikes, beyond the no-fly zone, were essential to stop Gaddafi.
Some in the Arab world sense a Gaddafi victory could turn the tide against pro-democracy movements that have unseated autocrats in Tunisia and Egypt and inspired mass protests in Bahrain, Yemen and elsewhere.
Gaddafi's Defense Ministry warned of swift retaliation, even beyond Libyan frontiers, against hostile action.
"Any foreign military act against Libya will expose all air and maritime traffic in the Mediterranean Sea to danger and civilian and military (facilities) will become targets of Libya's counter-attack," the ministry said in a statement.
Foreign military action could include no-fly and no-drive zones, a maritime exclusion zone, jamming army communications and intelligence help. Air strikes would almost certainly be launched to knock out Libyan radar and air defenses.
"Mission creep" worries some. Western powers, chastened by protracted wars in Afghanistan and Iraq, would be wary of getting drawn into any ground action in Libya.
Germany said it saw "considerable dangers and risks". NATO member Turkey also said it opposed the operation.
Gaddafi would be guilty of war crimes if he carries out a threat to attack civilians in Benghazi, the International Criminal Court's prosecutor Luis Moreno-Ocampo said.
Oil prices fell after the ceasefire announcement. Brent crude was 69 cents lower at $114.21 by 1352 GMT (9:52 a.m. EST).
(Additional reporting by a Reuters reporter in Benghazi, Michael Georgy in Tripoli, Mariam Karouny and Tarek Amara in Tunisia, Louis Charbonneau and Patrick Worsnip at the United Nations and John Irish in Paris; writing by Andrew Roche; editing by Giles Elgood)