Newburyport police are seeking a man in connection with a string of sexual assaults in that city over the past four months — the most recent on Monday night, police said.
In the Monday attack, a girl was walking to meet her boyfriend around 9:30 p.m., when a man came up from behind and sexually assaulted her near the intersection of High Street and Summit Place, said a spokesman for the Newburyport Police Department on Thursday.
The victim’s boyfriend, who was approaching, saw what happened and attempted to chase the suspect but was unable to catch up to him, police said.
The string of four attacks on four women and the girl since June appears to involve the same man, Newburyport police said in a statement Thursday.
The victim in Monday night’s attack did not require medical assistance, but police are still warning the public that the perpetrator is dangerous.
City Marshal Thomas Howard said the attacks were isolated, and it appears the victims did not know their assailant.
“This is a dangerous sexual predator who targets women with increasing audacity and violence, even striking women in well-lit areas and attacking two women at once in one case,” Howard said in a statement.
In each case, the perpetrator has been described as a white male in his 20s, about 6 feet tall, with brown hair, a normal build, and a skinny face, police said.
In addition to the Monday assault, the following attacks have been reported:
■ On June 22, a 20-year-old woman was attacked and groped on Merrimac Street while she walked home at 10:30 p.m.
■ On Sept. 9, a 23-year-old woman was attacked and sexually assaulted near the same Merrimac Street location, while she was walking home from the downtown area about 8:30 p.m.
■ On Sept. 25, two 23-year-old women were attacked and groped near the MBTA commuter rail entrance off Parker Street while they walked from the downtown area around 10:50 p.m.
Police urged anyone with information on the attacks to call them at 978-462-4411.
They also advised residents to walk in well-lit areas at night, ideally in pairs or with groups, and to not use headphones or mobile devices while walking.
“Newburyport continues to be a safe community, and the police department is working aggressively to identify and apprehend the individual behind these incidents,” Newburyport Mayor Donna D. Holaday said in the statement.
Trisha Thadani can be reached at trisha.thadani@globe.com. Follow her on Twitter @TrishaThadani.