Some of the Islamist militants behind the Easter Sunday bombings, that killed more than 250 people in Sri Lanka, are still at large and could be planning MORE violent attacks.

That’s according to U.S. ambassador to Sri Lanka — ALAINA TEPLITZ — who spoke to Reuters on Tuesday.

SOT: “…we do believe that there is active plotting underway and we have warned U.S. citizens and of course others who might read our warnings to be mindful of places that might make attractive targets for terrorists." despite scores of suspected Islamists arrested FOLLOWING THE BOMBINGS at three churches and four hotels - Sri Lankan security forces say they REMAIN on high alert amid intelligence reports — warning that militants are likely to strike AGAIN before the beginning of Ramadan on Monday.

Sri Lankan officials have acknowledged intelligence warnings from India BEFORE THE EASTER ATTACKS weren't shared widely enough(SOUNDBITE) (English) U.S. AMBASSADOR TO SRI LANKA, ALAINA TEPLITZ, SAYING:"The government of Sri Lanka has admitted lapses in intelligence and failures along the way, think that's a positive sign towards working to correct those lapses...”The FBI is now assisting Sri Lankan authorities in the investigation… but Teplitz declined to give more details.

ON MONDAY the media network for ISIS published a video IT SAID WAS its leader Abu Bakr al-Baghdadi – HIS FIRST APPEARANCE SINCE 2014 - in which he said the Sri Lanka bombings were THE WORK OF Islamic State.

The authenticity and date of the recording could not be independently verified.