Tripoli, Libya (CNN) -- The Libyan government vowed Friday to sink any ship approaching the besieged port city of Misrata, essentially threatening NATO patrols and humanitarian aid ships that have been bringing in food and medical supplies and ferrying out refugees and the wounded
Libya's threat came hours after NATO said it intercepted Libyan government forces laying mines in Misrata's harbor, which has been a lifeline for humanitarian aid in the months-long conflict between troops loyal to Moammar Gadhafi and rebels demanding an end to the dictator's four-decade rule. NATO-led forces began bombing regime targets in Libya last month after the U.N. Security Council approved a resolution authorizing any means necessary to protect civilians.
It also came as Gadhafi's forces were shelling Misrata in an attempt to re-enter the city after being pushed out by rebels. Misrata, the country's third-largest city, has been hemmed in on three sides for weeks by Gadhafi's forces, leaving the sea as the only escape route.
At least nine people were killed and another 30 were wounded in Friday's attacks in Misrata, said a doctor, who is a member of the medical committee in the city.
"There is an indiscriminate shelling now in Misrata," said the doctor, who asked not to be identified because he feared retribution by Gadhafi's forces.
Rebels accused Gadhafi forces of dismantling rocket launchers so they would escape detection by NATO forces during transport, and then reassembling for use in attacking civilians, a spokesman for the rebels said.
"We have reports that Gadhafi troops are loading fish boats with weapons in Tripoli and may be coming to Misrata," he said.
NATO personnel Friday stopped small boats carrying pro-Gadhafi forces who were laying anti-ship mines in Misrata's harbor, NATO spokesman Brig. Gen. Rob Weighill told reporters during a briefing in Brussels, Belgium.
NATO warships were in the process of disarming and clearing the mines that had been laid, he said.
Meanwhile, Libyan state TV announced that the Libyan military had successfully suppressed operations of the port.
"We will not allow any ship to dock at the port without being inspected by the Libyan government," Musa Ibrahim, a Libyan government spokesman, told reporters in Tripoli.
He said any aid to Misrata must be delivered through designated land routes.
Elsewhere, a senior rebel member, Omar al-Jernazi, told CNN that rebels "took complete control" Friday of Wazin -- a key Tunisian-Libyan border crossing -- after forcing Gadhafi forces to flee into Tunisia.
The Tunisian army allowed Gadhafi's troops to return to Libya at another border crossing, the rebel said.
Meanwhile, thousands more Libyans fled to Tunisia, stirring further concerns about a humanitarian crisis there, according to Tunisia's state-run news agency TAP, which cited Tunisian security sources. The U.N. High Commissioner for Refugees set up more tents in the Remada refugee camp, it said.
CNN's Frederik Pleitgen, Kareem Khadder and Saad Abedine contributed to this report.