ANKARA (Reuters) - A Turkish security official said Ankara saw “very strong signs” the gunman who killed Russia’s ambassador there on Monday was a follower of a U.S.-based Muslim cleric blamed for orchestrating a failed coup in July.

U.S. based cleric Fethullah Gulen at his home in Saylorsburg, Pennsylvania, U.S. July 29, 2016. REUTERS/Charles Mostoller/Files

A representative of cleric Fethullah Gulen, Alp Aslandogan, denied any link and said the exiled cleric condemned the murder as a “heinous act”.

The Turkish official, who declined to be identified, said the current investigation was focused on the gunman’s links to the network of Gulen’s followers, which the government calls the “Gulenist Terrorist Organisation” or “FETO”.

The government says Gulen, who has lived in self-imposed exile in the U.S. state of Pennsylvania since 1999, created a “parallel network” in the police, military, judiciary and civil service aimed at overthrowing the state. Gulen denies this.

President Tayyip Erdogan identified the attacker, who was later killed by security forces, as a member of the Ankara riot police who had spent 2-1/2 years on the force.

“The people he lived with before school were detained over FETO. It was determined that the people with whom he graduated from school were from a FETO team,” the senior security official said of the attacker.

“Information was obtained to the effect that people who helped him get into school were from FETO. There are very strong signs that the person who carried out this attack was from FETO. The investigation is currently focused totally on this.”

The official also cited the fact that the attacker had taken July 15-17 as holiday. The government may argue the timing of his holiday demonstrated foreknowledge of the July 15 coup.

Gulen adviser Aslandogan, who advises Gulen on media issues, said the allegations by the Turkish official were “laughable” and intended to cover up for lax security.

“Mr. Gulen categorically condemns this heinous act,” he told Reuters.