A man prays at a memorial after the deadly truck attack in New York. (Ricky Carioti/The Washington Post)

More than two days after authorities said a man with apparent allegiance to the Islamic State drove a truck onto a Manhattan bike path, killing eight and injuring a dozen others, the militant group declared that the attacker was a “soldier of the caliphate.”

This claim of responsibility late Thursday fell short of asserting that the Islamic State had coordinated or directed the attack, but instead suggested that the rampage was inspired by the militant group. Law enforcement officials in the United States had previously said as much, publicly saying the suspect appeared to be guided by Islamic State propaganda.

Federal authorities charged Sayfullo Saipov, a 29-year-old Uzbek immigrant, with carrying out the attack Tuesday, saying that it appears he was radicalized online sometime after coming to the United States in 2010. They say he chose Halloween to inflict maximum carnage, and he could potentially face the death penalty.

Precisely how the Islamic State responds to attacks can signify its possible level of involvement. After the 2015 attacks in Paris, highly detailed news releases were quickly distributed. But, in other cases, claims of attackers as a “soldiers” will follow only after media reports emerge publicly showing that suspect or suspects had declared allegiance to the group, which is also known as ISIS.

The Islamic State’s claim appeared to have resonated with President Trump, who paused a Friday morning tweetstorm largely focused on domestic politics to announce that the military had increased action against the group.

Trump emphasized this later Friday morning in remarks to reporters outside the White House, calling the suspected driver “an animal”and vowing to strike back “10 times harder” after Islamic State attacks.

“They claimed him as a soldier, good luck,” Trump said. “Every time they hit us, we know it’s ISIS, we hit them like you folks won’t believe.”

It was not immediately clear what Trump was referring to with his tweet suggesting the military had increased action since the truck rampage on Tuesday in Lower Manhattan.

Public data on military strikes against the Islamic State in Syria and Iraq did not show any increase in strikes since Tuesday. The U.S.-led coalition battling the Islamic State in Syria and Iraq releases daily summaries detailing activity in its air campaign over both countries.

These reports indicate operations have remained fairly consistent and, in fact, have subsided slightly since Tuesday’s attack. Coalition warplanes tallied 18 engagements with the Islamic State on Tuesday. On Wednesday and Thursday, there were 11 and 15, respectively. Separately, the Pentagon announced Friday that U.S. airstrikes had killed an unspecified number of Islamic State militants in Somalia.

After the truck attack in New York, authorities quickly turned to terrorism as a motive and said the driver had written notes referencing the Islamic State.

In the criminal complaint filed in federal court, the FBI said Saipov had reams of Islamic State propaganda on his cellphones. Saipov told authorities he was particularly inspired by a video of Islamic State leader Abu Bakr al-Baghdadi asking Muslims in the United States what they were doing to respond to the killing of other members of their faith in Iraq, the complaint states.

The Islamic State has urged adherents and followers to carry out attacks using vehicles such as trucks. As the group has suffered repeated losses on the battlefield and seen its self-declared caliphate shrink, terrorism by vehicle has become an attack of choice for supporters across the world. It has been used to deadly effect in France, Britain, Germany, Sweden, Spain and elsewhere.

The New York police said authorities continued Friday to sift through leads in the case as they investigated the attack.

“A lot of due diligence to do, going backwards through friends, associates, phone records, Internet contacts,” John Miller, the deputy commissioner of intelligence and counterterrorism at the New York City Police Department, said at a briefing.

Authorities said the New York suspect appeared to have closely hewed to the Islamic State’s guidance for carrying out such attacks. Saipov “appears to have followed almost exactly to a T the instructions that ISIS has put out in its social media channels,” Miller said during an earlier briefing.

Among other things, Miller said, that included the notes Saipov left behind declaring his allegiance. Court papers say one note, written in Arabic, could be translated in part to read: “Islamic Supplication. It will endure.”

After rampaging through the bike path in a rented Home Depot truck, police say, Saipov crashed into a school bus and got out. A police officer called to the scene shot and wounded him, and Saipov remains hospitalized. In the complaint, authorities said Saipov expressed pride in what happened and asked if he could display an Islamic State flag in his hospital room.

The Islamic State’s claim in this case was not made through the Amaq News Agency, which is linked to the group and often used to assert responsibility for attacks, but was offered in al-Naba, the group’s weekly newspaper, according to SITE Intelligence Group, which monitors extremist activity.

The group has claimed credit in the past for terrorist attacks committed by people who were inspired by its propaganda efforts but did not have any direct connections to anyone in the organization. It also asserted responsibility for the Las Vegas shooting rampage last month, although American authorities quickly dismissed that.

Andrew deGrandpre contributed to this report, which has been updated.

Further reading:

Sayfullo Saipov’s behavior behind the wheel of an empty truck raised suspicion before attack