Trump tweeted: "At least 7 dead and 48 wounded in terror attack and Mayor of London says there is 'no reason to be alarmed!'"
After the third attack in less than three months, Prime Minister Theresa May said Thursday's election would go ahead.
The president wrote a string of tweets in the aftermath of the London Bridge attack that left seven people dead.
Like the Bataclan and Manchester Arena, Borough Market was targeted for being a place of celebration and joy.
The arrests were made in connection with Saturday's attack that killed seven.
On social media, people reported being told to go into bars and restaurants and and take cover under tables.
Coverage of the Manchester attack reflected continued struggles for the mainstream media in covering terrorism.
ISIS claimed responsibility for the shooting via its Amaq news agency.
Philippine authorities say there's no evidence of terrorism in the attack which left 36 dead and dozens wounded.
Earlier, President Donald Trump said Washington was closely monitoring what he described as a "terrorist" attack unfolding in Manila.
Somalia's Al-Qaeda affiliate killed 4,300 people in 2016, making it Africa's biggest militant threat.
The U.K. Home Office told British media that an investigation into foreign sources of funding for local radical Islamist groups is "very sensitive."
The army has used airstrikes and street combat, yet still the Maute Group Islamist militants fight on.
The State Department's Stuart Jones appeared took a 20-second-long silent pause when a reporter asked him about U.S.' backing of democracy and Saudi Arabia
The attack took place near the entrance to the German embassy.
The lingering "stigma" of the Fourth Circuit's travel ban ruling
The army has used airstrikes and street combat to try and force out the Maute group militants who took hold of the city a week ago.
John McCain said in an interview that Donald Trump makes him feel nervous "from time to time."
John Kelly, Secretary of Homeland Security, said the move would be part of a broader effort to tighten airline security to combat what he called "a real sophisticated threat."
The summit of Group of Seven wealthy nations pitted Trump against the leaders of Germany, France, Britain, Italy, Canada and Japan on several issues.
Until the West crushes ISIS's ideology, bombings like the one in Manchester are going to continue—and maybe become more common.
Manila has deployed helicopters and commandoes to retake Murawi from jihadists.