According to the reporter, missiles crossed into Syria through Lebanon.
The apparent attack came days after the US, France and Britain conducted a coordinated missile attack against Syrian government targets.
"None of the combined aircraft or missiles involved in this mission were successfully engaged by Syrian air defenses and there is no indication Russian air defense systems were deployed", EUCOM said in a press release. Reports of that attack had been swirling on social media before the announcement.
The military announced at around 1.10am local time (11.10pm GMT) that it had fired missiles towards the Shay'rat Airbase, to the south-east of Homs, and its surrounding area in the Homs Governorate.
The raid in Homs countryside reportedly coincided with another missile attack against a military airbase near Damascus.
Observatory chief Rami Abdel Rahman said missiles did not hit any of the air bases.
Shayrat air base was targeted by United States forces in 2017 after a suspected chemical attack in Khan Sheikhoun that Washington blamed on the Syrian government.
Syrian air defences intercepted missiles over Homs which targeted Shayrat air base late on Monday night, Syrian state television reported.
Israel has previously carried out air strikes during the conflict in Syria, targeting Iran-backed militias fighting alongside the forces of Syrian President Bashar al-Assad.
The US Department of Defense said there was "no USA military activity in that area at this time".