DAMASCUS (AFP) - World powers piled pressure on Syria to allow observers to monitor spiralling deadly violence as activists condemned rights violations on Saturday's anniversary of International Human Rights Day. Activists said 41 civilians were killed on Friday in flashpoint cities across Syria as the opposition warned the regime was planning a "massacre" in the protest hub of Homs, where another civilian was killed on Saturday. "The world celebrates human rights as human rights are being violated in Syria," the opposition Syrian Revolution 2011 said in a message posted on its Facebook page. UN Human Rights Commissioner Navi Pillay has said that at least 4,000 people have been killed in a government crackdown on dissent in Syria since the anti-regime protest movement started in March. Pillay is to brief the UN Security Council about Syria and the wider Middle East at a meeting on Monday -- her second address to the world body since August when the number of dead was estimated at more than 2,000. "Now it is more than 4,000. Lives could have been changed if action had been taken sooner. It is not for me to determine what kind of action, it is for the Security Council," she told a UN news conference on Friday. Syrian President Bashar al-Assad has refused to let investigators from two UN human rights inquiries enter Syria, and his regime is resisting Arab League calls to accept monitors despite being hit by crippling sanctions. As the death toll mounted Britain and the United States expressed fresh concerns, and Washington urged Syria to allow independent monitors into the country. Damascus, which blames "armed terrorist gangs" for the violence, meanwhile appealed to the international community to help it find an "honourable exit" to the crisis and stem the flow of weapons into Syria. "We are appealing to the outside world and our brothers in the Arab world to help Syria (prevent the) channelling (of) weapons" into the country, foreign ministry spokesman Jihad Makdisi said on Friday, speaking in English. "If we all work together we can find an honourable exit to the crisis." The Syrian Observatory for Human Rights said at least 41 civilians, including seven children, were shot dead by Syrian security forces in the capital Damascus and the restive central city of Homs on Friday. Thirteen people were killed in the Homs region, five in the restive city of Hama, 18 around Damascus, two in Daraa, cradle of the protest movement, and three in the northwestern province of Idlib, the watchdog said. Thousands of Syrians took to the streets across the country on Friday in response to calls by pro-democracy activists who urged citizens to turn out in support of a "dignity strike... which will lead to the sudden death of this tyrant regime." Activists also called for a campaign of civil disobedience from from Sunday, the first day of the working week in Syria, with sit-ins at work, the closure of shops, universities and later a general strike. The Local Coordination Committees, which organises anti-regime protests on the ground in Syria, said the campaign would "snowball" and the strike is "the first step in an overall civil disobedience" campaign to overthrow the regime. The opposition Syrian National Council warned of a looming bloody final assault on Homs using the pretext of what the regime had called a "terrorist" attack Thursday on an oil pipeline. "The regime (is) paving the way to commit a massacre in order to extinguish the revolution in Homs," said the SNC, a coalition of Assad opponents. Homs, an important central junction city of 1.6 million residents mainly divided along confessional lines, is a tinderbox of sectarian tensions that the SNC said the regime was trying to exploit. Witnesses in Homs, already besieged for months by government troops, have reported a buildup of troops and pro-regime "shabiha" militiamen in armoured vehicles who have set up more than 60 checkpoints, the SNC said. US State Department spokeswoman Victoria Nuland said that Assad would be responsible for any further deaths. "There are reports today that the government may be preparing a very serious new assault on the city of Homs in a very large-scale way," said Nuland. London echoed Washington's concern, with Foreign Office minister Alistair Burt saying: "The Syrian government should immediately withdraw its forces from Homs and exercise restraint." An Arab League ministerial task force had been due to meet in the Qatari capital to mull a response to Syria which wants the bloc to lift sanctions in return for allowing in observers to monitor its deadly unrest. But reports from Doha and from Cairo, where the pan-Arab bloc has its headquarters, suggested the meeting on Syria would be held in mid-December.