Sri Lanka attack death toll rises to 290

Before the blasts on Sunday, a memo warned of a potential attack and requested heightened security, a police source tells CNN.

The memo was dated April 11 and was signed by Sri Lanka's deputy inspector general of police.

Sri Lankan Minister of Telecommunication Harin Fernando tweeted a picture of the memo on Sunday.

"Some intelligence officers were aware of this incidence. Therefore there was a delay in action. What my father heard was also from an intelligence officer. Serious action need to be taken as to why this warning was ignored. I was in Badulla last night," he wrote.

CNN obtained a copy of the memo. Here's what it says:

When you look at Sri Lanka in Google Maps, you see red dots with exclamation points marking the locations where the attacks happened on Sunday -- in the cities of Colombo, Negombo and Batticaloa.

Clicking on one of those red dots yields phone numbers for emergency services, including the police hotline, the fire department, ambulances and tourist police.

There's also a hotline to assist families of foreign nationals who have been affected by the attacks. The victims include citizens of at least eight other countries in addition to Sri Lanka.

The Department of Homeland Security said it's not aware of any credible or active threats in the United States as of now.

In a statement responding to the attacks in Sri Lanka, Homeland Security Acting Secretary Kevin McAleenan said the department is monitoring the situation and "doing all it can to protect the homeland from potential violent extremists."

"DHS stands resolutely with persons of every faith who look to worship in safety and peace. We will continue our work with partners around the world to ensure that all are able to worship without fear," the statement read.

As a precaution, the New York Police Department is implementing heightened security measures at houses of worship across the city. New York State police are also increasing patrols at religious institutions.

US Vice President Mike Pence called the attacks in Sri Lanka "an attack on Christianity & religious freedom everywhere," and said that he and President Donald Trump were monitoring the situation.

".@POTUS and I are monitoring the horrific attacks on those celebrating Easter in Sri Lanka. Our hearts & prayers are with the victims & their families. This atrocity is an attack on Christianity & religious freedom everywhere. No one should ever be in fear in a house of worship," Pence wrote on Twitter.

No one has claimed responsibility for the attacks yet, and the Sri Lankan government blocked social media sites, including Facebook and Instagram, while investigations are taking place.

Facebook has been working to identify and remove content that violates its standards, according to a statement from a company spokesperson. The company also said it was working to support law enforcement and first responders.

Here's the statement in full:

Sri Lanka's Tourism Development Authority has requested that hotels in the country take maximum measures to strengthen security.

Three luxury hotels in Colombo, the Cinnamon Grand, Shangri-La Hotel and The Kingsbury, were targeted in the blasts on Sunday morning. By the afternoon, a hotel in front of the Dehiwala Zoo in Dehiwala-Mount Lavinia had also been attacked.

The agency also urged the public to refrain from sharing unverified information about the attacks.

The Eiffel Tower will turn off its lights starting at midnight tonight to pay tribute to the victims of the attacks in Sri Lanka.

The first wave of attacks in Sri Lanka struck at the heart of the country's minority Christian community during busy Easter services at churches in the cities of Colombo, Negombo and Batticaloa on Sunday morning.

This photo taken at St. Sebastian's Church in Negombo is a snapshot of the horror that many experienced during this holy weekend. Blood stains are splattered across the walls and on a statue of Jesus Christ.

People from at least eight countries were killed in the series of attacks on churches and hotels in Sri Lanka, including:

Secretary of State Mike Pompeo said that several US citizens were among those killed, though he did not say how many.

In addition, the Sri Lankan Foreign Ministry said in a statement earlier that nine foreign nationals were reported missing and that 25 unidentified bodies at the Colombo Judicial Medical Officer's mortuary were believed to be foreigners.

At least 207 people have been killed and hundreds more are injured.