Seoul's subway operator will introduce brand new trains equipped with free mobile phone chargers and wider seats for pregnant women starting later this month, officials said Friday.

Seoul Metro, the operator of the capital's vast subway system, will put five new trains comprising 40 passenger cars into operation on Line 5 starting this month and add 20 more trains to the line by the end of this year, officials said.

The new trains make less noise and offer wireless phone chargers for the first time among Seoul subways.

A total of eight chargers will be installed in four passenger cars per train -- two in the middle and two with designated spots for wheelchairs.

The upgraded trains will also offer a more comfortable ride by increasing the width of each seat to 48 centimeters from 43.5 cm while making the previously seven-seat sections into six-seat sections.

Seats reserved for pregnant women, colored in pink, will be bigger, with a width of 53 cm.

Seoul Metro also decided to install four air quality improvement devices per passenger car, saying the move can lower fine dust levels inside cars by 21.2 percent on average.

Seoul Metro began replacing old subway trains with new ones starting on Line 2 in 2014. The renovation project for the line will be completed this year, and the operator plans to also give a makeover to old trains running on Line 4 and Line 8.

The operator is in charge of most lines from 1-9 on the Seoul Metropolitan Subway system. (Yonhap)