President Bashar al-Assad is fighting the greatest challenge to four decades of rule by the Assad family in Syria. Here is an overview of the protests, which have reportedly left 1,100 people dead, hundreds more injured and thousands under arrest.
What prompted the protests in Syria?
Syrians have endured decades of economic hardship, political repression and corruption under the rule of the Assad family, in power since 1971. President Bashar al-Assad - who inherited power from his father Hafez in 2000 - had moved to open up the country's economy, but continued to jail critics of the regime and maintained a stranglehold on the internet and media.
Political parties and protests were banned and the emergency law - in place since 1963 - gave the authorities sweeping powers of arrest.
The protests kicked off in mid-March, inspired by the revolutions that toppled the leaders of Tunisia and Egypt.
They began in the southern town of Deraa, where several teenagers were jailed for spray-painting the popular revolution slogan, "The people want the fall of the regime", on the wall of their school compound.
Residents protested, calling for the release of the children and chanting "God, Syria, Freedom". Security forces opened fire on the protesters, killing and wounding several. Days of unrest followed, with police shooting more people and protesters burning government buildings.
The turmoil in Deraa quickly spread to other towns and cities, including the third-largest city of Homs and Baniyas on the Mediterranean coast. Protesters have been calling for greater freedom, an end to corruption, and increasingly - the toppling of President Assad.
How has the government responded? What is the extent of the crackdown?
Early on in the protests, President Assad, 45, appeared on television promising to speed up reforms. In a major concession, he lifted the hated emergency law on 21 April. But days later, he resorted to overwhelming force to try to put down the protests.
The government has sent tanks and troops into at least nine towns and cities. In Deraa and Homs - where protests have persisted - the government has used tank fire to shoot down unarmed protesters, amateur video footage shows. Snipers fire from rooftops on residents who dare to venture outside. Men are rounded up and detained in house-to-house night-time raids. Electricity and communication lines are cut. Roads are blocked and hospitals raided. Journalists and UN observers are barred.
Troops have now moved on the northern town of Jisr al-Shughour, after the government said 120 security personnel were killed there, prompting more than 2,000 people to flee to Turkey.
Human Rights groups say about 1,100 civilians have been killed and thousands arrested since pro-democracy protests began on 18 March. Several hundred members of the security forces are also believed to have died. The government says it is pursuing "armed gangs" and "terrorist groups".
The government has also announced plans to draft a new election law, but critics have dismissed it as a cosmetic move.
How close is Syria to the tipping point?
Correspondents say the protests have not reached the critical mass - as seen in Egypt, Tunisia, or even Yemen.
The major cities of Damascus and Aleppo have seen small pockets of unrest, but confined to the suburbs or university campuses, due in part to a heavy security presence. And the protest epicentres of Deraa, Baniyas and Homs appear to have been silenced - for now - by a heavy military onslaught.
But there are conflicting reports about the recent violence in Jisr al-Shughour, with opposition groups saying it was sparked by a desertion from military ranks. The deserters were then shot by loyal troops, they said.
President Assad also has his supporters. There have been massive pro-Assad rallies in the capital, organised by the government in a show of force. Some of the smaller protests at university campuses have been met by rival pro-government demonstrators.
How is Syria different from Egypt or Libya?
There are several factors that complicate the crisis in Syria.
- Mr Assad enjoys strong support within many segments of Syrian society, mostly among minorities, the middle class and the business elite.
- There are fears of a civil war if President Assad should fall. Syria is made up of a precarious mix of confessions - 74% Sunni; 10% Christian, 10% Alawite, 3% Druze and 3% Other Shia. Even among those who want to see serious reforms, many would prefer to give President Assad time to implement them.
- Unlike in Egypt, there is no daylight between the army and the regime. The armed forces are overwhelmingly made up of Alawites, so they too are in a fight to maintain their power and privilege. While there have been reports of low-level defections, the military command appears solid.
- Syria is a major regional power and any chaos here will cause knock-on effects in countries such as Lebanon and Israel, where it can use proxy groups such as Hezbollah and Hamas to cause trouble. It also has close ties with Shia power Iran - an arch foe of the US and Israel - which could potentially draw Western powers into a dangerous Middle Eastern conflict.
How has the West responded and should more be done?
The US and EU have strongly condemned the Syrian government's violence against its own citizens and slapped sanctions on a number of senior Syrian figures.
On 18 May, the US imposed sanctions for the first time on President Assad himself, accusing him of human rights abuses. At the start of June, US Secretary of State, Hillary Clinton, called for President Assad to reform or "get out of the way". However, the Obama administration has no real levers with which to influence the Assad regime.
Western officials say they cannot act robustly because - unlike with Libya - they do not have the backing of the Arab League, which has remained silent on the issue of Syria.
The UN Security Council is also split, with France and the UK proposing a resolution to condemn the crackdown, but nations including Brazil, China and Russia voicing concern that such a resolution could inflame tensions.
They also argue that they have no clear picture of Syria after Mr Assad. In the absence of any clear opposition leaders who could unite its rival political, religious and ethnic communities, there are fears the country would descend into chaos.