BAGHDAD- Islamic State militants have restated their loyalty to the group's leader Abu Bakr al-Baghdadi, in what is believed to be their first public pledge of allegiance to him since his "caliphate" in Syria and Iraq collapsed last year.

The group continues to carry out bombings, ambushes and assassinations in both countries, as well as in Libya. However, Baghdadi's whereabouts have been unknown since the cross-border "caliphate" he declared in 2014 disintegrated with the fall of Mosul and Raqqa, its strongholds in Iraq and Syria respectively.

"To infuriate and terrorise the infidels, we renew our pledge of loyalty to the commander of the faithful and the caliph of the Muslims, the mujahid sheikh Abu Bakr al-Baghdadi al-Hussaini al-Qurashi may god preserve him," militants said in a statement posted on their social media groups.

Hisham al-Hashimi, who advises several governments including Iraq's on Islamic State affairs, said this was the first known pledge of loyalty to Baghdadi since Iraqi forces recaptured Mosul in July and an alliance of Kurdish and Arab militias took Raqqa in November, in both cases backed by a U.S.-led coalition.

There have been conflicting reports over whether Baghdadi, an Iraqi, is still alive.

However, Hashimi told Reuters that he was believed to be hiding in the vast desert area that straddles the Syria-Iraq border,

U.S. airstrikes killed most of his top lieutenants, including Islamic State's "war minister" Abu Omar al-Shishani, "governor of the Iraqi region" Abu Muslim al-Turkmani, group spokesman Abu Mohammed al-Adnani and "governor for Syria" Abu Ali al-Anbari.

(Reporting by Maher Chmaytelli; editing by David Stamp) ((maher.chmaytelli@thomsonreuters.com; +9647901917030;))