Libyan rebels are being helped to smuggle weapons through Tunisia to fight Col Muammar Gaddafi's forces in western Libya, the BBC has learned.
One Libyan smuggler told the BBC that AK-47 rifles and grenade launchers were being taken across the border in small but frequent consignments.
Other equipment being smuggled included Milans - a type of wire-guided anti-tank missile - machine guns, sniper rifles, and night-vision goggles.
Pro-Gaddafi forces are on the Tunisian border, and shelling often spills over.
The fledgling Tunisian government is fearful of giving overt support to the rebels, and Tunisian border guards are under orders to search each car going in to Libya.
But members of the Libyan diaspora are funding the purchase of small arms to send to western Libya, said the Libyan smuggler, who agreed to speak on condition of anonymity.
The smuggler said it was not a professional operation, but was carried out with the help of Tunisians sympathetic to the Libyan rebels.
The weapons are destined for towns in the Nafousa mountains, where rebels are fighting to wrest control of the west from Col Gaddafi.
While Benghazi in the east has sent weapons to rebel-held coastal enclaves like Misrata, the Nafousa mountains are landlocked.
Rebel Commander Ahbeel Dody, who we met on his way through Tunisia back into the mountains in the West, said a shortage of weapons in the Nafousa mountains was prolonging the war.
Towns in the area have gained ground in frequent clashes with Col Gaddafi's forces.
'Need heavier weapons'
"We are still mostly relying on what we can seize in battle from Col Gaddafi's forces," says Cdr Dody, who commands 500 men and has been visiting wounded fighters in Tunisian hospitals.
"It would be better if Nato sent us more and heavier weapons officially."
He says he and the other rebel commanders have a registration programme in which they record the serial number of each weapon and the name of the fighter it is given to, so the weapons can be collected when the war is over.
The BBC cannot independently verify that a record of weapons going to rebels fighters is being kept.
"When we win, we will collect all the weapons for the new Libyan army, we will not keep them," says Cdr Dody. "I want to get back to my work of building houses."
Among his fighters are the manager of a local bank and a pensioner.
But any flow of weapons through its territory is clearly of concern to Tunisia's interim government.
It has its own fledgling revolution to protect. It is dealing with strikes and demonstrations, trying to organise elections and establish security and stability in the aftermath of its uprising.
And the Tunisian government is wary of going against Col Gaddafi, especially with his forces taking positions so close to its borders.
"Our wives are terrified by the shelling from Col Gaddafi's forces," one resident of the dusty Tunisian town of Dahiba said. "The rockets come right across the border at night."
One man shows me a battered silver rocket, grey and glinting in the sunlight.
The men in Dahiba say their income from cross-border trade has dried up because of the war.
"We haven't been able to plant or water our fields either because they are too close to the shelling," one of them says.
The taxi drivers and restaurant owners have been affected too.
There are not many European pensioners taking the aquarobics class at the hotel pool, and there is no haggling to be heard at the souvenir stalls.
Tourism in Tunisia is down by 50%.
Yet Tunisian families are opening up their homes to provide free lodging for the bulk of 130,000 Libyans who have fled the fighting.
A Libyan charity co-ordinator, Oum Kaltoum, breaks down in tears when she takes me to meet a Tunisian seamstress who has had six Tunisian families to stay for more than two months now, three families to a room.
Tunisian towns cannot bear the strain much longer, says Nader Elhamessi from World Medical Camp Libya.
Libyan refugees have increased the population of one town, Tataouine, by half.
"That's a lot of electricity, water, food and medicine to pay for," says Mr Elhamessi. "It's just not sustainable, people will start to resent it and there will be incidents."
The tensions are already visible. The trademark Land Cruiser vehicles favoured by members of Col Gaddafi's government and entourage can be seen driving along the seafront at Djerba, with its ice-cream parlours and its plush hotels.
Tunisians joined Libyans to stage a protest outside a hotel where Col Gaddafi's wife and son were known to be staying.
The odd fight breaks out too. In the border town of Ben Gardane, there were clashes between pro- and anti-Gaddafi Tunisians on Sunday.
Many Tunisians who have lost their income because of the Libyan war say they support the rebels.
"Freedom has no price, the Libyan rebels are our brothers," says Habib Haj Abdallah, a resident of Dahiba, as he stands with a group of men and boys gathered on the hillside to watch for Col Gaddafi's rockets.
They have scrawled the name Bab al-Azizya on the wall, after Col Gaddafi's compound in Tripoli which is bombed regularly by Nato forces.
Whether they support the Libyan revolution or not, the Tunisians I have met from the capital in the north to the border in the south say the same thing.
"If the Libyan revolution fails, we will suffer more than the Libyans." Why? "Because Tunisia was the spark."