Gulf Arab states and the governments of France and Italy have withdrawn their ambassadors from Syria in protest as violence against civilians continues to intensify.
Activists in Syria described the "desperate medical situation" unfolding in Homs as civilian areas continued to be "shelled every few minutes".
At least 74 people were reported to have died on Monday after attacks by President Bashar al-Assad's forces.
Responding to the violence, the six-member Gulf Cooperation Council (GCC), which is made up of Saudi Arabia, Bahrain, Kuwait, Oman, Qatar and the United Arab Emirates, said that their ambassadors had been withdrawn "immediately" and added all Syrian envoys had been expelled.
"The Kingdom of Saudi Arabia, current head of the council, announces that the GCC states have decided to withdraw all their ambassadors from Syria and also demand that all ambassadors of the Syrian regime in its lands leave immediately," the GCC said in a statement.
King Abdullah of Saudi Arabia called on countries to "protect innocent lives and end the bloodshed" earlier this week.
The French and Italian foreign ministries also said their ambassadors would be withdrawn from Syria for "consultations", but added their embassies would stay open.
The UK withdrew its ambassador on Monday, while the United States closed its embassy in the country.
But even as pressure on the government mounted, the Russian foreign minister arrived in Damascus to meet President Assad and was greeted by cheering crowds waving pro-regime flags.
Meanwhile reports of attacks by government forces on civilians continued to emerge from Homs, with Sky News reporter Stuart Ramsay describing horrific scenes of violence inside civilian homes.
Injured fighters from the "outgunned" Free Syrian Army were described stumbling into houses, with some dying of their wounds.
Ramsay reported that one fighter who had been shot through the heart fell into a building and died immediately of his wounds.
Global protest network Avaaz said that at least 74 people were killed in Homs on Monday, most in the Baba Amr section.
Many more who have been injured could die because of low quantities of medical kits, beds, doctors and nurses.
Describing a "desperate medical situation", Avaaz told the Huffington Post UK that Baba Amr and Khaldiya were "still being shelled every few minutes".