The thwarted attack came after three other simultaneous assaults killed scores of security personnel in the lawless southern Al-Qaeda stronghold of Shabwa province, where Balhaf is also located.
Local and military officials have said 56 soldiers and policemen were killed in the three attacks.
State news agency Saba reported that 21 troops were confirmed dead and 15 wounded, but that the fate of "many" more was unknown.
"A 170-strong army force arrived at Balhaf" on the Gulf of Aden, the impoverished Arabian Peninsula country's only port for exporting liquified natural gas, the security official told AFP.
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Today's deadliest single attack was on an army camp responsible for ensuring security at Shabwa oilfields, the military said.
The two other attacks targeted an army checkpoint in Al-Nushaima area and a special forces camp at nearby Maifaa.
The defence ministry in Sanaa said a fourth Al-Qaeda attempt to detonate explosives targeting the Balhaf terminal ended in failure.
Security forces intercepted a vehicle which exploded, "killing the terrorists it was carrying," said the ministry's 26sep.Net news website, without specifying how many militants died.
AQAP has not yet claimed responsibility for the attacks.
Witnesses told AFP today that Yemeni jets flew over Balhaf and surrounding areas without carrying out any raids.
Last month, security was beefed up around Western embassies in Sanaa, and some were closed following warnings by Washington of an imminent attack.