A family of four with two young children were among 18 migrants found on boats in the English Channel near the Kent coast in the early hours of Thursday morning.
A Border Force cutter intercepted the first small boat about four miles south east of Folkestone as it headed towards the UK, at about 4am, the Home Office said.
The five men found on board, who said they were Iranian, were taken to Dover and handed to immigration officers.
About an hour later, the cutter found a second boat with 13 people on board two miles south of Folkestone.
There was a family of four on board – father, mother and two young children – and nine other men. They said they were from either Iran or Iraq.
It comes a day after 14 migrants, including two children, who said they were from Iran and Iraq, were also found off the south coast.