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.
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NEW: Libyan government threatens to sink aid ships
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NEW: NATO says Libyan forces intercepted while mining port
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At least nine dead, 30 wounded, a doctor says
"We have reports that @placeholder troops are loading fish boats with weapons in Tripoli and may be coming to Misrata," he said.