The United Nations’ human rights chief has said that government shelling of Syrian cities may amount to war crimes and should cease immediately.Navi Pillay, the UN High Commissioner for Human Rights, addressed the Human Rights Council on Monday as reports emerged of plans for Russia to send warships to the Syrian port of Tartus, the site of a Russian naval base."The government of Syria should immediately cease the use of heavy armaments and shelling of populated areas, as such actions amount to crimes against humanity and possible war crimes,” Navi Pillay told a meeting of the Human Rights Council on Monday.Pillay said those responsible for attacks on UN observers in Syria should be brought to justice after the organisation’s mission to the country was suspended last week due to what it called an intensification of violence.A UN convoy trying to reach Al-Haffe town last week came under fire and was forced to turn back by a stone-throwing crowd."We must make our utmost possible efforts to ensure accountability for all perpetrators, including those who have attacked UN observers in Syria,” Pillay said.Russia’s Interfax news agency said on Monday that two Russian navy ships would sail to Tartus to protect Russian citizens and its base there, quoting an unidentified Russian navy official, but did not give a precise date.The official said the ships would carry an unspecified number of marines to protect Russians in Syria and evacuate materials from Tartus, Russia’s only naval base outside the former Soviet Union, if necessary.Russian President Vladimir Putin is due to meet Barack Obama, his US counterpart at a G20 summit to discuss differences over what to do about the bloody conflict.Russia has shielded Syria’s regime from international sanctions over its crackdown on protests as well as continuing to provide it with arms.Shelling in HomsMeanwhile, activists reported renewed shelling on several neighbourhoods in the central city of Homs."Shelling and shooting renewed in Homs city, with explosions heard in the Khaldiyeh neighbourhood,” the Britain-based Syrian Observatory for Human Rights said.