"The rebels are now nine kilometres (six miles) away from Hama military airport, which they want to put out of action," said Rami Abdel Rahman of the Syrian Observatory for Human Rights.
A rebel leader in the area, Yusef al-Hassan, said the airport was important because "that is where the regime makes its barrel bombs, and warplanes take off from there to carry out air strikes".
Barrel bombs have killed hundreds of civilians, especially in rebel areas of the divided northern city of Aleppo, in recent months.
The takeover of the checkpoint in Tarabih comes on the back of Sunday's capture of a weapons depot in the area.
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"The regime has suffered several defeats in Hama province in recent days," said Abdel Rahman.
As they have advanced, rebels have cut off the road linking Hama city, the provincial capital, to a string of regime-controlled Christian and Alawite villages in the west of the province, he added.
Hassan said the regime was sending reinforcements.
"They are stepping up their troop presence here, which will limit the regime's capabilities in other areas," the rebel leader told AFP via the Internet.
The air force has used barrel bombs to hit opposition-controlled areas for months.
In Aleppo alone, air strikes since December have killed hundreds of civilians and forced thousands of families to flee.
Rights groups have hit out at the regime for using the crude bombs, which they describe as failing to discriminate between civilian and military targets.
A barrel bomb strike on a rebel-held village in Daraa province Monday killed an elderly man, his daughter and her three grandchildren, said the Observatory.
In Aleppo itself, rebel today detonated two explosives-filled tunnels under a regime-held building, leaving "13 dead among the guards and regime forces" and wounding an unspecified number of others, the Observatory said.