DAMASCUS  - Twin bombs exploded outside the Palace of Justice in Damascus on Thursday as deadly violence raged across the country and Turkey deployed missile batteries along its volatile border with Syria.On the political front, world powers were preparing for a crucial meeting on ways to end the conflict and to discuss a plan by peace envoy Kofi Annan for an interim government.The meeting in Geneva, agreed only after wrangling between Moscow and Washington over the agenda and the guest list, will be attended by some regional governments but not by rival Middle East heavyweights Iran and Saudi Arabia.Annan spokesman Ahmad Fawzi said delegates of countries attending the talks would gather in Geneva on Friday for a "preparatory meeting."Russia has already poured cold water on Saturday's meeting, with Foreign Minister Sergei Lavrov saying Moscow rejects Western pressure for the ouster of President Bashar al-Assad.Lavrov also said it was a mistake to exclude Syria's ally Iran from Saturday's crunch meeting of world and regional powers. Thursday's heaviest toll was in the northern Damascus suburb of Douma where 18 civilians, 12 from one family, were killed when troops clashed with rebel fighters, said the Syrian Observatory for Human Rights.Turkey has sent missile batteries, tanks and troops to the border as a "security corridor" after Syria shot down a Turkish warplane last Friday, media reports said. There was no official confirmation, but state-run TRT television showed dozens of military vehicles reportedly heading for the border, in a convoy that included air defence systems.About 30 military vehicles accompanied by a truck towing missile batteries left a base in the southeastern province of Hatay for the border, about 50 kilometres (30 miles) away, Milliyet newspaper reported.The Turkish Phantom F-4 jet was downed by Syrian fire over the eastern Mediterranean in what PM Recep Tayyip Erdogan said was a "heinous attack" over international waters. UN-Arab League envoy Kofi Annan will demand "irreversible" steps by President Bashar al-Assad and the Syrian opposition to end the country's conflict, according to a copy of his transition plan obtained by AFP. A blueprint for multi-party elections and an offer for "significant" international funding to rebuild Syria will also be discussed at a meeting of foreign ministers from the major powers and other key countries in Geneva on Saturday.With the battle between Assad's forces and opposition groups becoming more bitter by the day, the special envoy's plan says it is "essential that any settlement provides for clear and irreversible steps in the transition according to a fixed time frame."Annan calls for a "transitional government of national unity" to establish a "neutral environment" for the transition, according to the plan, given to AFP by diplomatic sources.The interim government "could include members of the present government and the opposition and other groups, but would exclude from government those whose continued presence and participation would undermine the credibility of the transition and jeopardize stability and reconciliation.Diplomats have said this means that Assad could be ruled out of the government but did not automatically exclude his participation. It could also mean certain opposition figures would be kept out of the transition authority.Assad's future is likely to be a key part of the Geneva talks when US Secretary of State Hillary Clinton will negotiate with Russia's Foreign Minister Sergei Lavrov, along with the foreign ministers of Britain, France, Russia, Qatar, Turkey and Kuwait.Russia is Syria's last major international ally and Lavrov said Thursday that "foreign players should not be dictating their solutions to the Syrians. We do not and cannot support any intervention or solutions dictated from abroad."Annan's transition plan calls for a "national dialogue process" which he insists must be "meaningful." "That is to say its key outcomes must be implemented."He says there must be a review of the constitution and legal system "subject to popular approval.""Once the new constitutional order is established, it is necessary to prepare for and conduct free and fair multi-party elections for the new institutions and offices that have been established," the document says.But Annan, who agreed a six point peace plan with Assad that has not been carried out, stresses that the conditions for a political settlement must be put in place now."There must be an end to bloodshed. All parties must re-commit themselves credibly to the six-point plan. This must include a cessation of armed violence in all its forms and immediate, credible and visible actions" to carry out the plan.Both sides must "engage genuinely" with Annan and name "effective" negotiators to work on a settlement."The organized international community, including the members of the Action Group stands ready to offer significant support for the implementation of an agreement reached by the parties," says the document."This may include an international assistance presence under a United Nations mandate if requested. Significant funds will be available to support reconstruction and rehabilitation."