A suspected war criminal who allegedly played a key role in the slaughter of 40,000 civilians in Sri Lanka has landed a cushy job at the United Nations — with full diplomatic immunity.

Human-rights groups are outraged that Shavendra Silva, 46, a top ex-military commander, was named Sri Lanka’s deputy permanent UN representative in August, after which he moved to New York.

His arrival came a year after his troops defied international pleas and shelled a no-fire zone packed with women, children and elderly refugees, according to observers.

Silva also stands accused of mowing down a group of separatist political leaders who agreed to surrender and were waving white flags when they were shot.

“It’s a slap in the face,” said an investigator familiar with Silva, who last year oversaw the final months of a brutal 26-year civil war against Tamil separatists on the island nation off India’s southeastern tip.

The war started in 1983 after the Tamils, a Hindu ethnic minority, were denied power by the ruling Sinhalese, Buddhists, and formed a violent resistance group, the Tamil Tigers.

Full story: ‘War criminal’ has immunity with UN gig – NYPOST.com