The armoured vehicle stood at Cameroon's Garoua-Boulai border crossing, the barrel of its machine gun pointing unmistakeably towards the Central African Republic.
Here, police say they are on maximum alert after rebels attacked a crucial highway in the CAR, blocking hundreds of trucks and prompting an exodus of terrified people into Cameroon.
An alliance of armed groups tried to advance on the CAR capital Bangui ahead of presidential elections on December 27.
The gunmen were swiftly thwarted by UN peacekeepers, the CAR army and Rwandan and Russian reinforcements.
But they then switched tactics, trying to strangle Bangui by launching hit-and-run raids on the RN1 highway, the lifeline linking the city to Cameroon.
Garoua-Boulai, 725 kilometres (450 miles) west of Bangui, is a border town of 80,000 people where before the crisis around 200 trucks rolled across each day, laden with essentials for the landlocked CAR's capital.
The border point has now become a parking lot -- more than 400 trucks are stacked up, waiting to cross.
A couple of weeks ago, some truckers ventured over, but swiftly turned back because of the poor security.
"The border is now closed," a senior police official told AFP, speaking on condition of anonymity.
- Troops and police -
Soldiers from the elite Rapid Intervention Brigade have taken up position at the edge of the border perimeter to tackle any rebel incursion.
In the town, police have stepped up patrols and identity checks in the street, even in hotels and bars, and take away people who are unable to produce an ID.
The attacks on CAR's supply backbone are the latest crisis to roil a country that ranks second poorest in the world and has seen little but bloodshed and misery since a coup seven years ago.
In 2016, voters selected a technocrat, Faustin Archange Touadera, as their first president following the coup.
He was declared victor in the December 27 vote, but in highly disputed circumstances.
The result accounts for only half of registered voters. Around two-thirds of the country is in the hands of armed groups that sprang up in the turmoil in 2013, and many citizens were unable or too scared to cast their ballot.
So far, there have been no shortages in Bangui, but the impact of a de-facto blockade is starting to be felt in higher prices for certain foods, and supermarkets and wholesalers say that their stores are starting to dwindle.
In Garoua-Boulai, hundreds of trucks are parked on the roadside, and hundreds more on land in front of a government building, the sub-prefecture.
The night watchman is Oumarou Tougou, who patrols with a torch in his hand. "I go around to prevent theft," he said.
Nickson, a young Cameroonian "moto-boy", or driver's mate, was lying on a sheet under his truck, his face barely lit by his mobile phone.
"I've been sleeping here for 21 days," he said. "it gets cold at night and we don't have much to eat."
Gabin, a 22-year-old "moto-boy" from the CAR, blew on a fire to warm up a pot of food. He was cooking for a group of 44 drivers and their assistants.
Some of the drivers had come very far.
They included 17 truckers hauling fuel from Chad, a thousand kilometres away, and heading for Bangui.
"It's impossible -- they have to make the road secure," said one of them, Abdel Habid.
- Refugee flow -
Just a few weeks ago, hundreds of Central Africans in the nearby refugee camp of Gado-Badzere crossed the border post each day to return home.
These days, the flow has been reversed, as their compatriots seek the haven of Cameroon. Four thousand have crossed, according to the UN's refugee agency.
Hundreds were waiting in front of an old building in Garoua-Boulai to sign up for aid.
A 22-year-old woman, Vanessa, tried to calm her four-month-old baby.
They had arrived after a 300-kilometre trek by motorbike from the village of Babou.
"We fled when the rebels attacked," she said.
A heavily pregnant woman, Loraine, said she had arrived in Cameroon after trudging through the bush, fear stalking every step -- her father, she said, "works with the customs service," and she was terrified of reprisals by the gunmen.