Turkish police stand guard outisde the Reina nightclub by the Bosphorus, which was attacked by a gunman, in Istanbul. REUTERS/Huseyin Aldemir

ISTANBUL (Reuters) - Mechanical excavators on Monday demolished most of the Istanbul nightclub where a gunman killed 39 people on New Year’s Day in an attack claimed by Islamic State, after the city municipality ordered its partial demolition.

Reuters TV footage showed wooden debris piled high across the area where the exclusive Reina club stood along the Bosphorus shore, below a suspension bridge linking Europe and Asia. Only the entrance area of the club remained standing.

The Istanbul city council said in a statement the decision was taken to demolish parts of the nightclub because they violated regulations.

State-run Anadolu news agency cited Reina employees as saying they were unaware of the demolition decision and arrived in the morning to see the destruction.

Police on Jan. 17 captured the alleged gunman, an Uzbek national they said had clearly acted on behalf of Islamic State. The jihadist group claimed credit for the attack, saying it was revenge for Turkish military involvement in Syria.

The attacker opened fire with an automatic rifle, throwing stun grenades to allow himself to reload and shooting the wounded on the ground. Among those killed in the attack were Turks and visitors from several Arab nations, India and Canada.

Last month, the United States revealed that a secret military ground operation killed an Islamic State operative, a close associate of leader Abu Bakr al-Baghdadi, who was linked to the Istanbul nightclub attack.