Story highlights Kantner had been kidnapped previously by Somali pirates

Militants' deadline for $600,000 ransom passed on Sunday

(CNN) A German man has been beheaded by Abu Sayyaf militants in the southern Philippines after a deadline to pay his ransom passed.

Philippine and German officials confirmed that 70-year-old Jurgen Kantner had been killed after being held for three months by the Islamist militant group.

It was the second time Kantner, 70, had been abducted. He was held along with his partner, Sabine Merz, by Somali pirates for nearly two months in 2008.

German national Jurgen Kantner and his partner, Sabine Merz, in 2009, months after they were freed by Somali pirates.

Abu Sayyaf posted a gruesome video of its militants killing the man with a curved knife. The video was distributed by the SITE Intelligence Group .

"The Federal Chancellor condemns the abominable act, which once again shows how unscrupulous and inhumane these terrorists are. We all must stand together and fight against them," German Chancellor Angela Merkel's spokesman Steffen Seibert said.

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