BOSTON -- Two men were arrested by Massachusetts Bay Transportation Authority police and charged with assault in incidents in the Red and Green lines.

In the first incident, a Revere woman was on a Green Line trolley Monday night near Copley Station when she felt someone grab her buttocks. She turned to her friend and asked if she touched her, and heard a man say, "I did it. And I liked it," according to a police report.

The woman told the man to stop, but he responded, "You will never see me again, so what does it matter?"

Officers apprehended the man at Park Street Station. He was identified as William Carlyle, 52, of Boston.

In the second incident, a woman said she was groped while boarding a Red Line train in June 2009 at the Quincy Center Station. She said she felt a man grab her buttocks, and when she confronted him, he verbally harassed her.

The man was identified as James Williams, of Chelsea, and was taken into custody at Quincy Center Station Monday night.

The arrests come one day after the MBTA launched a renewed effort to fight sexual harassment on trains and buses.