The border between Poland and Lithuania is strategically important because its seizure would cut off the Baltic states from the rest of the Western alliance.
Figures released by Mayor of London Sadiq Khan show as many as 20 incidents per day.
Khuram Butt and Rachid Redouane were "warned about their conduct" after wrestling in the water.
The final opinion polls show a healthy lead for the Conservative Party but were badly wrong two years ago.
U.S.-U.K. relations have become a hot topic during the general election campaign.
The divisions in the East End community have turned it into a flashpoint between white nationalists and radical Islamists.
Police have already named the other two attackers as Khuram Butt and Rachid Redouance.
After the third attack in less than three months, Prime Minister Theresa May said Thursday's election would go ahead.
The arrests were made in connection with Saturday's attack that killed seven.
Across the Arab world, changing demographics, a lack of basic rights and Western interventions all drive young people toward extreme violence.
Suicide bomber Abedi was one of 20,000 people known to MI5 but not one of the 3,000 people under active investigation.
The New York Times posted leaked images of the remnants the suicide bomber's device on Thursday.
Ramadan Abedi denies his son's involvement in the attack on Manchester Arena.
The Tory Party's manifesto heightens the chance of drawn out negotiations and the hardest of Brexits.
The 37-year-old was due to board a flight for Turkey Tuesday evening.
Abedi blew himself up with an improvised explosive device, killing 22 after an Ariana Grande concert.
Top spies say European security services are more disciplined than their U.S. counterparts.