Syria state media say militants have attacked a military post belonging to the government forces in the country's northwest, setting off clashes that killed three soldiers.

The state-run Ikhbariya TV says the militants were disguised as farmers from the area in the attack early on Tuesday and approached the military post outside a de-militarized zone in Idlib province.

The TV says the soldiers clashed with the militants, who blew themselves up, killing three soldiers.

The Syrian Observatory for Human Rights also reported the attack. The Observatory and a media group, Idlib Correspondent, said the jihadi Ansar Tawheed group was behind the attack.

It's the latest breach of a months-old Russia-Turkey negotiated truce in Idlib and surrounding areas. Recent violence has strained the truce, which also includes a de-militarized zone.