The International Committee of the Red Cross (ICRC) has classed Syria's conflict as an internal armed conflict - a civil war in layman's terms. The humanitarian agency said the violence had broken out of its three original flashpoints of Homs, Hama and Idlib.
– ICRC spokesman Hicham Hassan
There is a non-international armed conflict in Syria. Not every place is affected, but it is not only limited to those three areas, it has spread to several other areas. That does not mean that all areas throughout the country are affected by hostilities.
The classification means that anyone who commits certain crimes against civilians can be charged with war crimes in violation of international humanitarian law.
The UN monitoring team in Syria has released video of observers visiting Tremseh to investigate an assault on the village by Syrian forces.
Fighting within Damascus city is "the fiercest yet" residents have told Reuters news agency.
There have been many reports of loud explosions and persistent gunfire in south Damascus.
Special envoy Kofi Annan will travel to Moscow on Monday for two days of talks with the President Vladimir Putin and Foreign Minister Sergei Lavrov on the crisis in Syria, a spokesman has confirmed
Several people have been injured after an explosion hit a bus carrying security forces in Damascus. Residents say they heard a powerful blast, followed by the sirens of ambulances rushing toward Damascus's southern ring road near the neighbourhood of Midan.
Activists say the blast appeared to have been caused by an explosive device stuck onto the bus.
Iran says it is ready to host talks between the Syrian government and opposition groups:
– Ali Akbar Salehi, Iranian Foreign Minister
The Islamic Republic of Iran is ready to sit down with the Syrian opposition and invite them to Iran. We are ready to facilitate and provide the conditions for talks between the opposition and the government.
– SYRIAN FOREIGN MINISTER
Yesterday we received a letter from [UN envoy] Kofi Annan addressed to the Foreign Minister Walid al-Moualem. The least that can be said about this letter about what happened in Tremseh is that it did not rely on facts. As diplomatically as possible, we say that this letter was very rushed."
Syria's Foreign Ministry has denied claims by the UN's envoy Kofi Annan that helicopters, tanks and artillery were used in clashes in Tremseh. It says 37 fighters and two civilians were killed - and not over 100 as activists say.