Police arrested a 38-year-old man in connection to the Manchester suicide bombing in an operation at London's Heathrow Airport, according to a Greater Manchester Police statement.
The statement said 19 people had been arrested in the investigation so far but 12 of these had been released without charge.
In a separate development, a 30-year old man was arrested in Ilford, east London on suspicion of the commission, preparation or instigation of terrorist acts, police said.
Prime Minister Theresa May signaled more concrete action against terror suspects in a speech on Tuesday in which she said she would review human rights laws to make it easier to deport foreign terror suspects and "restrict the freedom and movements" of those that presented a threat.
May said she also planned "longer prison sentences for those convicted of terrorist offences".
She said if human rights laws "get in the way" of tougher measures, that legislation would be changed.
Security has become the dominant issue in election campaigning since the Manchester concert bombing carried out by 22-year-old Salman Abedi.
The May government has come under scrutiny about previous police cuts and failures by the country's security services to stop suspects who were known to the authorities.
Main opposition leader Jeremy Corbyn has called on May to resign.
Criticisms peaked after reports claiming Italy's intelligence services had warned their British counterparts about the third attacker from Saturday's London Bridge killings, Moroccan-Italian Youssef Zaghba.
May said the U.K.'s domestic intelligence services would carry out a review after calls about how the authorities dealt with information regarding the attackers.
Khuram Shazad Butt, 27, one of the three terrorists shot dead by police on Saturday, had taken part in a Channel 4 program called The Jihadis Next Door last year.
