The two women - Gao Huayun, 29, from China and Marcy Dayawan, 40, from the Philippines - were kidnapped from the Singamata Reef Resort in Malaysia's Sabah state on April 2 in a late-night raid by gunmen and taken to the southern Philippines.
Najib said the women were brought back to Malaysia after being rescued, stressing that no ransom had been paid to secure their release.
"Success due to cooperation of Malaysia and Philippines security forces," Najib said on Twitter yesterday, adding Malaysia would help Gao return home "as soon as possible".
Another Chinese national, a 34-year-old fish farm manager, was kidnapped early this month by gunmen along the same coastline.
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China-Malaysia relations have already been tested over the Malaysia Airlines flight MH370 that vanished on March 8 with 239 people aboard - two-thirds of them Chinese.
Chinese relatives of passengers have harshly accused Malaysian authorities of ineptitude and a cover-up.
Sabah's eastern coast - known for its pristine beaches and dive sites popular with tourists - has seen a string of violence, including a bloody armed assault last year by Islamic guerillas from the nearby southern Philippines.
Abu Sayyaf has been blamed for the kidnapping of 21 people, including several foreign tourists, from another Sabah diving resort in 2000.
Twenty of those hostages were released within five months, reportedly after hefty ransoms were paid. A Filipino captive was held until 2003.