U.S. President Barack Obama spoke to Prime Minister Stephen Harper by phone Wednesday, expressing his country’s solidarity with Canada and offering assistance in the wake of the attacks in Ottawa that left one soldier dead Wednesday.

Speaking with reporters inside the Oval Office, Obama described his phone conversation with Harper, which took place hours after two shooting attacks occurred on Parliament Hill in the nation’s capital.

Obama said he pledged to ensure national security efforts continue to be co-ordinated between the two countries in light of the attacks.

“We have to remain vigilant when it comes to dealing with these kinds of acts of senseless violence or terrorism and I pledged as always to make sure that our national security teams are coordinated very closely,” Obama said. “Not only is Canada one of our closest allies in the world, but they're our neighbours and our friends.”

Obama said Harper was “very appreciative of the expressions of concern by the American people.”

The president also said he was reminded of how “warmly” he was received during previous visits to Ottawa.

“So obviously we’re all shaken by bit, but we’re going to do everything we can to ensure that we’re standing side by side with Canada at this time.”

Obama said it is not yet known what motivated the shootings.

According to a statement from the White House, Obama condemned the “outrageous attacks” in his phone conversation with Harper. The president was referring to both Wednesday’s shootings on Parliament Hill and the attack on two soldiers in Quebec on Oct. 20.

As a massive police presence remained on the streets of the nation’s capital on Wednesday afternoon, a source confirmed to CTV News that the “FBI is assisting the case,” but no other details were provided.

A U.S. official said the Department of Homeland Security and U.S. law enforcement are “monitoring the evolving situation” in Ottawa.

FBI spokesperson Paul Bresson said that although there is no indication of a threat to the United States in light of Wednesday’s attacks, the agency is taking certain precautions.

“FBI has reminded our field offices and government partners to remain vigilant in light of recent calls for attacks against government personnel by terrorist groups and like-minded individuals,” Bresson said.