Islamic State sympathizers are posting celebratory memes online following a terrorist attack on Parliament and Westminister Bridge in London this morning.

Around 2:40 p.m. local time, London police responded to reports of a a stabbing at Parliament.

The attack sent Britain’s Parliament into lockdown after an attacker stabbed an officer and was then shot by police. Around the same time, witnesses reported a vehicle targeting pedestrians on nearby Westminster Bridge. Aerial photos show a car crashed into the bridge railing near injured people.

Prime Minister Theresa May was at Parliament as the attack began, but her spokesman told Reuters that the PM was safe.

At a press conference, London police announced that 4 were dead, including the attacker and a police officer. 20 others were injured.

As of now, Scotland Yard has stated that they are treating the attack as terrorism until they declare it not to be. The attack follows reports of “increased jihadi chatter” after the UK’s adoption of an electronics ban aboard flights from certain Muslim-majority countries, writes the AP. The New York Times reports that the U.S. has also adopted the ban, which affects people’s abilities to carry laptops as carry-on. Airports in 10 Muslim-majority countries are affected by the laptop ban, including Egypt, Jordan, Saudi Arabia, Kuwait, Morocco, Qatar, the United Arab Emirates, Lebanon, Tunisia, and Turkey.

The new law requires people are these countries to put their laptops in checked baggage.

The attack also comes the same day as U.S. Secretary of State Rex Tillerson hosts 68 foreign ministers from all countries involved in the Global Coalition to Counter ISIS in Washington, D.C. The UK is included in this summit, reports ABC.

It’s currently unconfirmed if the attack was orchestrated or inspired by the Islamic State. Terrorism analyst Michael S. Smith II reports that ISIS channels are talking about the attack, but have not claimed it. SITE Intel director shared the above meme from an ISIS terrorist channel showing Big Ben burning.

However, reports of a driver running down pedestrians on Westminister Bridge does fit ISIS’ M.O.

In an ISIS magazine article from November 2016, ISIS suggested to jihadists how to carry out a successful attack as a lone wolf operative. In the article, ISIS said that a lone wolf should use a vehicle to plow into a crowd and to carry a secondary weapon.

Soon after, an ISIS-inspired student carried out vehicular attack on Ohio State University. The perpetrator, Somali-born Abdul Razak Ali Artan, also carried a machete. ISIS later claimed the attacked and named Artan as one of their “soldiers.”

A similar attack claimed by ISIS was carried out on July 14, 2016 at a Bastille Day celebration in Nice, France by Mohamed Lahouaiej Bouhlel. Bouhlel is responsible for murdering up to 84 people by ramming into them with a truck and shooting at them.

More recently, another vehicular attack was carried out on a Christmas market that killed 12 and injured 48 at Breitscheidplatz in Berlin-Charlottenburg, Germany. The Islamic State also claimed this attack.

Heavy is an independent news organization. We report acts of terror and violence so that the public may be fully informed. This may include content considered graphic, which is identified. We do not support, in any way, the individuals or organizations involved.

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