BRUSSELS, April 24 (Reuters) - NATO said on Friday it would extend a month-long anti-piracy mission off Somalia until June 20 and cancel port visits to Singapore and Australia.

A four-ship task force will resume operations in the Gulf of Aden after concluding a brief visit to Karachi in Pakistan because of the worsening impact of piracy on shipping in the region, NATO spokeswoman Carmen Romero said.

The task force had been due to conclude its mission off Somalia last Thursday. It will not now make planned port visits to Singapore or Australia, she said.

Ambassadors of the 28-nation military alliance took the decision to extend the one-month mission at a meeting in Brussels.

Somali gangs have made millions of dollars seizing vessels in the Gulf of Aden and the Indian Ocean, driving up insurance rates and other costs in key sea lanes linking Europe to Asia.

The attacks have worsened despite the presence of naval forces from more than a dozen states, including task forces under NATO, EU and U.S. command.

A NATO spokesman said earlier this week that alliance Secretary-General Jaap de Hoop Scheffer was pressing for tougher rules to allow the detention of captured suspects.

But restoring stability to Somalia itself is generally seen as the only long-term solution to the problem of piracy in the region. (Reporting by David Brunnstrom, editing by Tim Pearce)

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