Syrian state TV claimed that the strikes, which hit near the country's eastern border just after midnight on June 18, were carried out by USA aircraft, wounding dozens of Syrian Army soldiers and Iranian-backed Iraqi Popular Mobilization Forces paramilitary fighters deployed to nearby positions at Albu Kamal and At Tanf.
The Syrian Observatory for Human Rights said unidentified planes had struck Lebanon's Shi'ite Hezbollah and other allied foreign militias around Albu Kamal.
A drone attack by the US-led global coalition killed 40 Syrian soldiers and allies and injured 30 in a desert area south of al-Bukamal, northeastern of Deir Ezzor province, on Monday.
The official said the drone bombed Iraqi faction positions between Syrian military positions and Albu Kamal and Tanf.
Israel is also suspected of carrying out numerous raids on Syrian government positions and Hezbollah weapons caches over the years, and last month announced unprecedented strikes on what it said were Tehran-operated bases in Syria.
The coalition's press office said it had heard reports that a strike in the area of Al-Hari had killed and wounded members of a pro-regime Iraqi group, but denied it was responsible. There were no immediate details on casualties.
The U.S. -led coalition uses air power and special forces to back an alliance of Syrian Arab and Kurdish militia fighting Islamic State northeast of Albu Kamal.
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The U.K. -based war monitor said the strikes killed 40 people.
"No member of the U.S. -led coalition carried out strikes near Albu Kamal", said Major Josh Jacques, a U.S. Central Command spokesman, to Reuters.
Israel maintains a formal policy of non-intervention in the Syrian civil war but continuously asserts that it will not allow Iran to entrench itself in the country, where it has for years provided military backing to Assad alongside Russian Federation.
Asked about the reported air strikes, an Israeli military spokeswoman said: "We do not comment on foreign reports".
Israel, alarmed about the clout of arch enemies Iran and Hezbollah, has been pressing Russia, Assad's other key ally, to make sure they do not entrench their military sway in Syria.
"We will take action - and are already taking action - against efforts to establish a militarily presence by Iran and its proxies in Syria both close to the border and deep inside Syria".