UN chief demands 'hostile acts' in Middle East to be ended

UN Secretary-General Antonio Guterres is urging an immediate halt to "all hostile acts" to avoid "a new conflagration" in the Middle East, after Israeli forces bombed Iranian targets inside Syria.

Israel says the strikes were retaliation for an Iranian rocket barrage on its positions in the Golan Heights and has called on the UN Security Council and secretary-general to immediately condemn Iran's attack.

The Security Council, deeply divided over Syria, is highly unlikely to issue a statement and as of Friday morning no council member has asked for a meeting.

This comes after Israeli airstrikes across Syria killed at least 23 fighters, including five Syrian regime troops and 18 other allied forces overnight on Thursday.

The UK-based Syrian Observatory for Human Rights said that an officer was included in those killed from regime troops, and that other casualties included Syrians and foreigners. 

Thousands of Lebanese, Iranian and Tehran-backed Afghani, Pakistani and Iraqi fighters operate in Syria.

Russia's defence ministry said that Israel had used 28 planes in raids over Syria and fired a total of 70 missiles.

"[Twenty-eight] Israeli F-15 and F-16 aircraft were used in the attack, which released around 60 air-to-ground missiles over various parts of Syria," the ministry said in a statement. 

"Israel also fired more than ten tactical ground-to-ground missiles."

Iranian forces in Syria reportedly fired around 20 rockets and missiles at Israeli army positions in the occupied Golan Heights.

Israel and Iran have long fought each other through proxies, and with the new exchange each seemed to be sending a warning that a direct clash between them could swiftly escalate.