From the bloody repression of pro-democracy demonstrations to the rise of jihadists and intervention by regional and world powers, here are 10 key developments in Syria's devastating civil war.

The twin bombings of churches in Egypt suggest that Islamic State group jihadists are lashing out as they find themselves coming under increasing pressure in Iraq and Syria, analysts say.

The group's Egyptian affiliate which claimed Sunday's attacks in the Nile Delta cities of Tanta and Alexandria has been centred in the Sinai Peninsula, where it has killed hundreds of policemen and soldiers.

In the Syrian town of Khan Sheikhun, site of an alleged chemical weapons attack, residents still mourning their dead on Friday welcomed U.S. strikes as a way to pressure Damascus.

US missiles targeted Syrian forces Friday in response to a suspected chemical attack that killed up to 86 people earlier this week.

It was the first direct US strike against the government of President Bashar al-Assad in Syria's devastating six-year war.

From strong messages of support to fierce condemnation, here are the main global reactions to a US strike on a Syria air base in response to a suspected chemical attack. 

- Against -RUSSIA: Unsurprisingly, the main ally of Syrian President Bashar al-Assad was robust in its opposition to the strike.

An air strike hit rebel-held Khan Sheikhun in northwestern Syria on Tuesday morning, leaving dozens of civilians dead from a suspected chemical weapons attack.

Gently placing flowers outside a Saint Petersburg metro station to honour the 14 people killed in Monday's devastating suicide bombing, Ksenia Zashikhina ponders what might have been.

Warplanes carried out a suspected toxic gas attack on a rebel-held town in northwestern Syria on Tuesday, killing at least 58 people, the Syrian Observatory for Human Rights monitor said.

When America entered World War I, a century ago this week, the European powers were bogged down in a grinding trench war that had killed millions and ravaged the European continent.

Swinging its industrial might and vast manpower behind France and Britain against Germany and its allies on April 6, 1917, the United States tipped the balance of the conflict and marked its own emergence as a global power.

With his popularity battered by food shortages, economic chaos and rampant crime, it is hard to understand how Venezuelan President Nicolas Maduro has clung to power.