Syrian forces thrust into the rebellious city of Homs on Wednesday, killing as many as 100 civilians by the accounts of opposition activists, and Turkey appeared to be preparing a new diplomatic push against President Bashar al-Assad.

Prime Minister Tayyip Erdogan, who is readying an initiative uniting Western, Arab and other states which have called for Ankara's former ally Assad to step down, was due to speak to Russian President Dmitry Medvedev later on Wednesday.

The Turkish premier, who described the Russian and Chinese veto of the U.N. resolution at the weekend as a fiasco, faces a hard sell with Moscow. Prime Minister Vladimir Putin has condemned Western interference of the kind seen last year in Libya as a cult of violence.

Putin, who first won the presidency after his military assault on the rebel Russian city of Grozny, is expected to return to the Kremlin via an election next month in which the Russian leader accuses the West of aiding his opponents.

Moscow's foreign minister, having visited Assad in Damascus on Tuesday, made clear Russia was still opposed to any peace talks that were conditional on Assad first stepping aside.

A newspaper close to the Erdogan government said Turkey planned to organise a conference with Arab and Western governments in Istanbul, part of a broader initiative that may be outlined later on Wednesday. A NATO member and rising Muslim power in the region, Ankara is sheltering Syrian rebel army commanders and has spoken of creating safe havens for refugees.

As the diplomatic gears turned, the military offensive in Homs and elsewhere showed no sign of let up. Activists in the city also accused militiamen of slaughtering three families in their homes - the sort of incident that is fuelling fears of a descent into more widespread, Iraq-style sectarian killing.

The day's death toll stood at over 100, activists said, offering figures that could not be independently verified.

ASSAULT

The onslaught on Homs, one of the bloodiest of the 11-month-old revolt against Assad, has not relented despite a promise to end the bloodshed that the Syrian leader gave to Russia, which saved Damascus from U.N. Security Council action on Saturday.

In the latest assault on Homs, troops fired rockets and mortars while tanks entered the Inshaat neighbourhood and moved closer to Bab Amro, the district hardest hit by bombardments that have killed nearly 200 people in the last two days, activists in the city and opposition sources said.

A group known as the Syrian Revolution General Commission called in a statement in the afternoon for outside humanitarian protection and that the day's death toll stood at 100.

Hospitals were without electricity, it said, and were short of supplies, while the wounded and those transporting them to clinics perpetually risked arrest by the security forces.

Syrian state television blamed explosions on Homs militants laying charges. It accused terrorists of targeting a key refinery in the city with mortars while activists blamed the army for a fire that was filmed by residents.

Russian Foreign Minister Sergei Lavrov said countries with influence over the Syrian opposition should press them to enter a dialogue with Assad, comments that made clear Moscow had no immediate intention of abandoning its long-time ally.

Lavrov was speaking in Moscow a day after he met Assad in Damascus, where he said both nations wanted to revive an Arab League monitoring effort that was suspended due to violence.

French Foreign Minister Alain Juppe dismissed Syrian pledges of peace as deceit, and we're not going to fall for it.

Putin insisted Russia was acting in good faith and was wary of Western motives in Syria: We of course condemn all violence regardless of its source, but one cannot act like an elephant in a china shop, Putin told Russian religious leaders.

Help them, advise them, limit, for instance, their ability to use weapons but not interfere under any circumstances.

A cult of violence has been coming to the fore in international affairs in the past decade, he said.

MILITIAMEN

Syrian opposition figures, who said Lavrov had brought no new initiative, spurn Assad's promises of reform as meaningless while his troops are killing civilians and say he must go.

Walid al-Bunni, a senior member of the opposition Syrian National Council (SNC), dismissed Lavrov's dialogue proposal.

The Arab initiative is clear. Assad must step down and Syrians will then be ready to sit together at a table with whoever succeeds him to discuss a democratic transition, the head of the SNC's foreign policy committee told Reuters.

Western and Arab states frustrated by the Russian and Chinese vetoes of their draft U.N. resolution are seeking to isolate Assad and bolster those opposed to his 11-year rule.

Pro-Assad militiamen shot dead at least 20 civilians in Homs when they stormed their homes on the outskirts of opposition areas overnight, the Syrian Observatory for Human Rights said.

Rami Abdelrahman, who heads the British-based Observatory, told Reuters the unarmed victims were a family of five, one of seven and one of eight.

There was no immediate comment from Syrian authorities and the report could not be verified. The authorities have placed tight restrictions on access to the country.

Activist Hassan said bombardment intensified in the early morning, targeting the Sunni Muslim districts of Bab Amro, al-Bayada, al-Khalidiya and Wadi al-Arab, all hostile to Assad, whose minority Alawite sect has dominated Syria for five decades.

Mortar and rocket fire has subsided, but heavy machineguns and anti-aircraft guns are still strong, he said. Tanks are in main thoroughfares in the city and appear poised to push deep into residential areas.

State news agency SANA said funerals had been conducted on Tuesday for 30 members of the security forces.

Army deserters and insurgents, at least nominally commanded by officers based in Turkey, are fighting back against Assad's violent response to what began as a mostly peaceful protest movement and now threatens to slide into sectarian civil war.

DIPLOMATIC PRESSURE

Assad is seeing the civilised world turn against him and he thinks he will win if he uses more brutal force before the world could act, said Catherine al-Talli, a senior SNC member.

The attack on Homs has intensified Western and regional diplomatic pressure on Assad. The six members of the Gulf Cooperation Council recalled their ambassadors from Damascus on Tuesday and expelled Syrian envoys from their own capitals.

Australian Foreign Minister Kevin Rudd called in Syria's charge d'affaires Jawdat Ali on Wednesday and told him it was time for Assad to find an exit strategy before the situation in Syria degenerates further and more lives are lost.

Russia's veto of the Security Council resolution on Syria went beyond protecting an ally and arms buyer, analysts said. It showed Moscow's determination to crush what it sees as a Western crusade to use the United Nations to topple unfriendly governments.

The same holds true for China, which followed Russia's lead and joined Moscow in striking down a European-Arab draft resolution that would have endorsed an Arab League plan for Assad to transfer power to his deputy to prepare free elections.

There are all sorts of political interests involved but there is also a basic difference about whether the international community should be involved in internal conflicts against the will of the government, said David Bosco of American University in Washington.

(Additional reporting by Louis Charbonneau at the United Nations, Steve Gutterman in Moscow, Alistair Lyon and Dominic Evans in Beirut, John Irish in Paris and Yasmine Saleh and Ayman Samir in Cairo; Editing by Jon Boyle)