Libya: Nato says Gaddafi tried to mine Misrata harbour
Nato says its warships have intercepted pro-Gaddafi forces trying to lay mines in the harbour of the city of Misrata.
A senior Nato official said crews were disposing of the mines.
Rebels say government tanks have launched another assault on Misrata, which has been under siege for several weeks.
In another development, Tunisian troops are reported to have captured Libyan soldiers who crossed the border in pursuit of rebel forces.
Nato's director of operations in Libya, Brig Rob Weighill, said warships stationed in the Mediterranean stopped the mine-laying attempt on Friday morning.
"Our ships intercepted the small boats that were laying them and we are disposing of the mines that we found," he told reporters via video-link from his headquarters in Naples, Italy.
"It again shows [Libyan leader Col Muammar Gaddafi's] complete disregard for international law and his willingness to attack humanitarian delivery efforts," he added.
Nato is enforcing a UN resolution to protect civilians in Libya amid a two-month revolt inspired by other uprisings in the Arab world.
Human rights groups say more than 1,000 people have been killed in the fighting in Misrata and many more have been wounded.
The harbour has been a lifeline for ships ferrying the injured to hospitals in the rebel stronghold, Benghazi, and also for aid entering the city.
Brig Weighill added that rebels in Misrata had made advances in recent days.
"The rebels have expanded their perimeter significantly over the past week. To suggest they are winning would be overly optimistic," he said. "They are putting up a very spirited fight."'Tank attack'
Meanwhile, foreign journalists in Misrata reported loud explosions coming from the direction of the airport on Friday.
A rebel fighter helping a wounded comrade back from the front line told AFP news agency that four tanks had attacked the city "and one has been destroyed so far".
"They took up positions during the night on the airport road and tried to enter the city. We've stopped them at the outer limits, at least for now," he said.
In western Libya, the situation at the Wazin border crossing was said to be calm after fierce fighting saw it change hands twice in only a few hours. Rebels were said to be in control of it by Friday morning.
The crossing has changed hands several times in recent weeks.
Government troops who retook the post on Thursday chased rebel forces into the nearby Tunisian town of Dahiba, Tunisian TV said. The pro-Gaddafi forces were overpowered by Tunisian forces and surrendered their weapons.
Analysts say the to-and-fro fighting for the crossing is typical of the fluid and complex Libyan conflict that broke out in mid-February.
Tunisian TV said Libyan forces in about 15 vehicles entered Dahiba on Friday morning.
"The violation of [Tunisian] territories by Gaddafi brigades took place this morning during their heavy fight against revolutionaries," the report said.
"This caused a violent chaos including in the centre of Dahiba. While the national army and border guards dominated the brigades and confiscated their weapons, the residents of Dahiba and the surrounding areas threw stones at the brigades' vehicles to show that they objected to their entrance into the town."
A resident of Dahiba told Reuters that pro-Gaddafi forces fired shells into the town, damaging buildings and injuring at least one resident. A group drove into the town in a truck in pursuit of rebels, he said.
One report said Tunisian troops had fired into the air to disperse the pro-Gaddafi forces.
Tunisian authorities warned of a "dangerous military escalation".
"Shots fired at a populated area on Tunisian territory [are] a violation of Tunisia's territorial integrity and a violation of the security of the residents of this region," a statement from the Tunisian foreign ministry said.
"Given the gravity of what has happened ... the Tunisian authorities have informed the Libyans of their extreme indignation and demand measures to put an immediate stop to these violations."
Thousands of people have fled across Libya's borders to escape the violence of recent weeks.