Israel has shot down a Syrian fighter jet it claimed had breached Israeli airspace.

Today's incident came as advancing Syrian government forces who had retaken territory from rebels reached the Golan Heights frontier for the first time in seven years.

The Israeli military said it monitored the advance of the Syrian Sukhoi fighter jet and shot it down with a pair of Patriot missiles after it penetrated Israeli airspace by just over a mile.

Israeli prime minister Benjamin Netanyahu called the breach of Israeli territory a "gross violation" of a 1974 agreement that established the demilitarised zone between Israel and Syria.

Syria's military, however, said one of its jets had been targeted by Israel over Syrian territory as it flew sorties against Islamic State (IS) militants.

Syrian forces have been battling rebels and IS militants at the frontier with Israel for weeks in a campaign to restore President Bashar Assad's rule over south-western Syria.

Smoke trails from two Patriot missiles can be seen near the Israeli city of Safed in northern Israel today

It is the first time that Israel has shot down a manned Syrian fighter jet since 2014.

The army said there had been an increase in 'internal fighting in Syria,' including involving the air force, since the morning hours.

It said it was on 'high alert and will continue to operate against the breach' of a 1974 ceasefire agreement between the two countries.

Israel has been stressing for weeks that it would enforce the ceasefire between it and Syria amid a Russian-backed government offensive in the country's south.

'A short while ago, two Patriot missiles were launched at a Syrian Sukhoi fighter jet that infiltrated into Israeli airspace,' the Israeli Defence Forces (IDF) said in a statement.

'The IDF monitored the advance of the fighter jet, which infiltrated about two kilometres (1.24 miles) into Israeli airspace. It was then intercepted by the Patriot missiles.'

But, a Syrian military source accused Israel of firing at one of its warplanes as it carried out operations against jihadists over Syrian territory in the Golan Heights.

The source, cited by state news agency SANA, said Israel 'targeted one of our warplanes... in Syrian airspace'.

The Israeli military said the Syrian plane it shot down had departed from the Syrian T4 air base – which Israel is believed to have attacked earlier this year – and had crashed on the Syrian-held side of the Golan Heights.

Israeli military spokesman Lieutenant-Colonel Jonathan Conricus said: 'We do not have any information so far about the pilots. I do not know of any reports of parachutes being spotted, and we do not know if any pilots have been retrieved.'

Today's incident comes a day after Israel's air defences fired at Syrian rockets it feared could hit its territory

Israeli military spokesman Lieutenant-Colonel Jonathan Conricus said the aircraft crashed 'most likely in the southern part of the Syrian Golan Heights'. Israel occupies a large part of the Golan

Lt Col. Conricus said that the plane flew toward Israel at 'relatively high speed' before it allegedly breached the country's airspace.

It was not known whether the plane had deliberately crossed into Israel, he said, while confirming that the plane was Syrian, not Russian.

He added: 'The only thing we know about the aircraft is that it crashed, most likely in the southern part of the Syrian Golan Heights.'

An AFP correspondent said flames and smoke could be seen rising from the area of the fence between Syria and the Israeli-occupied Golan Heights.

Israel launched two Patriot missiles over Golan Heights to intercept a fighter jet, according to the military

Today's incident comes a day after Israel's air defences fired at Syrian rockets it feared could hit its territory.

Syrian troops have ousted rebels from a majority of the country's south, part of which borders the Israeli-occupied Golan, and are now closing in on a patch held by the Islamic State group.

The Damascus regime has long accused Israel of backing ISIS and other opposition factions.

'The Israeli enemy has confirmed its adoption of armed terrorist groups, and targeted one of our warplanes which was hitting them in the Saida region on the edge of the Yarmuk basin in Syrian airspace,' the military source said.

Photos shared on social media show the missiles being launched by Israel

The source, cited by state news agency SANA, did not specify if the plane had been hit or downed.

The town of Saida sits just inside Syrian territory, about one kilometre (less than one mile) east of the buffer zone with the Israeli-annexed Golan, and is held by ISIS.

Clashes were raging between regime troops and ISIS jihadists on the northern edges of the town on Tuesday, according to the Syrian Observatory for Human Rights, a Britain-based war monitor.

Israeli Prime Minister Benjamin Netanyahu (above) met with the Russian Foreign Minister, Sergei Lavrov, on Monday

Israel has been on high alert since June 19, when Syrian government forces launched the Russia-backed offensive to retake Quneitra and Daraa and provinces, adjacent respectively to the Israeli-held section of the Golan and to Jordan.

Israel has sought to avoid direct involvement in Syria's seven-year civil war, but it has acknowledged carrying out dozens of air strikes there to stop what it says are advanced weapons deliveries to Hezbollah, one of its enemies.

It has also pledged to prevent its arch-enemy Iran from entrenching itself militarily in the neighbouring country.

A series of air strikes that have killed Iranians in Syria have been attributed to Israel in recent weeks.

The strikes have led to condemnation from Syrian President Bashar al-Assad's regime, but Israel has maintained good relations with Russia and has coordinated its actions in Syria with Moscow.

Both Russia and Iran are backing Assad in the civil war.

Israeli Prime Minister Benjamin Netanyahu also met Russian Foreign Minister Sergei Lavrov in Jerusalem on Monday to discuss the Syrian conflict.

Russia offered to keep Iranian forces 100 kilometres (62 miles) away from the Israeli-occupied Golan, but Israel said the proposal did not go far enough.

'We won't accept Iranian military entrenchment in Syria, not near the border, not beyond the 100-kilometre stretch, which by the way the Russians talk about and agree to,' a senior Israeli official said, speaking on condition of anonymity.

'We said there are also long-range weapons beyond that distance, and all the forces must leave Syria.'

Israel seized 1,200 square kilometres (460 square miles) of the Golan Heights from Syria in the 1967 Six Day war, in a move never recognised internationally.

Israel activates 'David's Sling' missile defense system for first time to intercept Syrian rockets

The shooting down of the fighter jet comes a day after Israel activated a joint US-Israeli missile interceptor in response to rockets from the fighting in neighboring Syria, that were believed to be headed for Israeli territory.

The system, dubbed David's Sling, is meant to counter the type of medium-range missiles that Iran-backed Lebanese Hezbollah militants have and rounded out Israel's multi-layer aerial defense system when it became operational in 2017.

Its activation came after Israel on two separate occasions this month fired Patriot missiles at incoming drones from Syria.

The Israeli military said two interceptors were launched after rockets from the fighting in Syria were identified.

No injuries or damage was reported, and the military says the rockets landed in Syrian territory.

The interceptors were launched on the Syrian frontier, where Damascus's Russian-backed forces have been routing rebels.

Smoke can be seen following an explosion at the Syrian side of the Israeli Syrian border as it is seen from the Israeli-occupied Golan Heights, Israel, on Monday, July 23

The incident set off sirens throughout northern Israel and residents were forced to rush into shelters.

David's Sling's addition last year marked the completion of Israel's multi-tier system that includes the Arrow, designed to intercept long-range ballistic missiles in the stratosphere with an eye on Iran, and Iron Dome, which defends against short-range rockets from the Gaza Strip.

Israel evacuates 800 White Helmets heroes and their families from Syrian army advances so they can be resettled in Britain, Germany and Canada

An attempt to evacuate up to 800 White Helmets rescue workers in Syria to Jordan on Sunday, with the help of the Israeli military, was condemned yesterday by Damascus as a 'criminal operation'.

Nearly 300 White Helmets were left stranded in Syria after efforts to get them out of a war-torn region in the country failed.

The first responders were prevented from reaching an evacuation point in an escape operation.

Syria's civil defence unit, known as White Helmets, are trying to escape the country's war-torn region in the south into Jordan but up to 300 volunteers have been left behind. This file photo shows the group responding after air strikes on Douma in 2016

The UK has backed an international effort to rescue members of the group and their families via the frontier with the Israeli-occupied Golan Heights.

UK Foreign Secretary Jeremy Hunt said in a joint statement with Penny Mordaunt, the International Development Secretary, that the 'brave and selfless' volunteers required 'immediate protection'.

Jordan's foreign ministry announced in a statement that the kingdom received 422 Syrian citizens, after earlier saying it had given permission for 800 to arrive.

An Israeli soldier hands out water on a bus during the evacuation of White Helmets from Syria

It has been reported the remaining White Helmets could not reach Israeli-occupied Golan Heights due to fighting between ISIS and the Syrian regime.

The saved White Helmets rescue workers in Syria were evacuated with the help of the Israeli military and could be resettled in the UK.

The Syrian regime considers the White Helmets as a 'terrorist organisations' as they operate in areas controlled by opponents to Bashar al-Assad. The group fled the area near the southern border earlier this summer.

A convoy on its way from the Golan Heights as the Israeli army helped to rescue White Helmets

A video grab shows the evacuation of White Helmet rescuers in Syria on their way to Jordan

Founded in 2013, the Syria Civil Defence, or White Helmets, is a network of first responders which rescues wounded in the aftermath of air strikes, shelling or explosions in rebel-held territory.

On Monday Damascus condemned the evacuation, calling it a 'criminal operation.'

Jordan agreed to temporarily house 422 evacuees, although its Foreign Ministry said Britain, Germany and Canada would resettle them.

Family members of the Syrian WHite Helmet rescuers on a bus during the evacuation

Spokesman Mohammed al-Kayed said the Syrians would remain in a closed area for up to three months before moving on.

Israel carried out the rescue mission on Saturday night following a request from the 'US, Canada, and EU countries'.

It is unclear at this time just how many Syrian rescue workers could be relocated to the UK.

People are escorted to a bus by Israeli soldiers during the evacuation on Sunday

Mr Hunt and Penny Mordaunt said in a joint statement: 'Following a joint diplomatic effort by the UK and international partners, a group of White Helmets volunteers from southern Syria and their families have been able to leave Syria for safety.

'They are now being assisted by the UNHCR in Jordan pending international resettlement.

'The White Helmets have saved over 115,000 lives during the Syrian conflict, at great risk to their own. Many White Helmets volunteers have also been killed while doing their work - trying to rescue civilians trapped in bombarded buildings or providing first aid to injured civilians.

Israeli soldiers guiding members of families of Syrian White Helmet rescuers into a bus

'White Helmets have been the target of attacks and, due to their high profile, we judged that, in these particular circumstances, the volunteers required immediate protection.

'We therefore took steps with the aim of affording that protection to as many of the volunteers and their families as possible.

'We pay tribute to the brave and selfless work that White Helmets volunteers have done to save Syrians on all sides of the conflict.'