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.
Russian ships for Tartus
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.
In-depth coverage of escalating violence across Syria
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.
Meanwhile, 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 UK-based Syrian Observatory for Human Rights (SOHR) said.
Medical aid organisation Médecins Sans Frontières (MSF) has been seeking official authorisation from the Syrian government to deliver aid to cities that are most affected by the violence, including Homs.
MSF in negotiations
Bruce de la Vigne, MSF director of operations, told Al Jazeera that his organisation is "negotiating with Damascus about the delivery of much needed humanitarian aid to key locations in Syria".
In the eastern Deir Az Zor province, the SOHR said that four people, including a rebel commander, were killed in an explosion in the town of Mohassan.
Clashes and shelling reportedly also went on through the night in several areas of Damascus province, including the towns of Douma and Qoudsaya, under bombardment by regime forces for the past five days.
The Local Co-ordination Committees (LCC), an opposition activist network, said that Qoudsaya came under "heavy shelling" and that "snipers are shooting at any moving object."
Fares Mohamed, a member of the LCC in Zabadani, a town near Damascus, told AFP news agency via email that the Syrian army had "imposed a suffocating blockade" on the areas around Qoudsaya and a nearby town.
He said the shelling began after an anti-regime demonstration in Qoudsaya.
The activist added that "huge military reinforcements" had arrived in the town and that the wounded could not be treated due to the intensity of the shelling and sniper fire.
In the southern province of Deraa, one civilian was reported killed in overnight clashes between rebels and regime troops in the region of Al-Lajat.
Regime forces backed by aircraft overnight also pounded for more than seven hours a region known as the Kurdish Mountain in the northwest province of Latakia, forcing many residents to flee, the Observatory said.