Kidnappers in the southern Philippines have released a Filipino-American woman who has seized in July, but they continue to hold her 14-year-old son and a nephew.

Philippine officials say Gerfa Yeatts Lunsmann was set free late Sunday on Basilan island, a stronghold of militant Islamic groups including the notorious Abu Sayyaf group, which has links to al-Qaida.

It was not clear whether any ransom was paid to the kidnappers, who have not identified themselves. But Zamboanga Mayor Celso Lobregat told reporters there have been contacts.

Lobregat said Lunsmann was relieved to be free but still worried about her son.

Lunsmann, who lives in the United States, was visiting her home city of Zamboanga when she was kidnapped with her son and nephew on July 12.

The U.S. embassy in Manila thanked Philippine authorities for their help in securing Lunsmann's release.