On Saturday, Israel launched its second high-profile targeted assassination in the country in less than a month, killing the Iranian Revolutionary Guards' spy chief for Syria and three other Guards members.

Already unstable after years of civil war, Syria has seen attacks on US troops on its territory, Israel targeting its airports and senior Iranian figures, Iran striking suspected jihadists, as well attacks from Jordan and Turkey.

Here are some questions and answers about the upsurge in raids on the country.

Why is Iran getting involved?

Since the start of the Israel-Hamas war, sporadic fire has targeted the Israel-annexed Golan Heights from Syrian territory.

According to the Syrian Observatory for Human Rights, a Britain-based monitor which relies on a network of sources in Syria, these attacks have been carried out by Syrian fighters working with Lebanon-based militant group Hezbollah.

Like those targeting US troops, these attacks have not had a major impact.

However on January 8, Israel said it had killed a key figure from Palestinian militant group Hamas close to the Golan Heights who had been responsible for the attacks.

Israel also stepped up its regular air raids on pro-Iranian militias in Syria and targeted the airports in the capital Damascus and northern city of Aleppo.

Most of these strikes are "likely aimed at disrupting Iranian arms shipments to Hezbollah and to Iran-aligned groups inside Syria", said Lund.

In a heavy blow for Iran, senior Revolutionary Guards commander Razi Moussavi was killed on December 25 in what Tehran said was an Israeli strike near Damascus.

Who is targeting US forces?

The United States has bases in both Syria and Iraq. With Washington a key ally of Israel, the sites have faced almost daily attacks claimed by Iran-linked groups since outbreak of the war in Gaza.

There are about 900 US troops stationed in Syria and 2,500 in Iraq as part of a coalition of forces in the fight against the Islamic State (IS) group.

Between October 17 and January 17, at least 140 attacks by drones, rockets, mortars and short-range ballistic missiles on US and other coalition forces were recorded in both countries, according to a US defence official.

Eighty-three of these attacks were in Syria, but most have failed to hit their targets, according to the official, who reported no fatalities in Syria, and just one in Iraq.

The majority have been claimed by the Islamic Resistance in Iraq, a loose alliance of Iran-linked armed groups that oppose US support for Israel in the Gaza war.

The situation remains contained for now, however, as the United States and Iran are seeking to control the degree of violence and avoid a broader conflict.

"Both sides are certainly trying to manage the level of violence, but that's where the similarities stop," said Aron Lund from the Century International think tank.

"The United States would prefer to see no violence at all, but Iran and its allies... are deliberately raising the level of conflict."

They are trying to force Washington, either by forcing them to be drawn into the type of conflict that it had hoped to avoid or engage with their demands to rein in Israel in Gaza, he said.

Why is Iran launching strikes?

On January 16, Iran launched strikes on targets in Syria and Iraq in retaliation for a deadly suicide attack in Iran at the start of the month.

Tehran said the targets in Syria were linked to IS but AFP could not determine where the missiles had landed.

Experts believe Iran was seeking to flex its muscles but refrained from targeting US interests for fear of sparking a wider conflict.

Who else is involved?

Turkey launched a series of air strikes this month against Kurds who have established an autonomous administration in northeast Syria, as well as against Iraq's autonomous Kurdistan region.

Ankara said it has carried out strikes against Kurdish militants in northern Syria in response to the deaths of nine Turkish soldiers in clashes with suspected Kurdish militants in Iraq.

This week, Jordan is believed to have carried out strikes in Syria that killed nine civilians, including two children, the Syrian Observatory for Human Rights and a media outlet reported.