Pickpockets are using earphone cords as 'fishing lines' to steal smartphones in crowded MTR carriages and stations, police warned. And indecent assaults and covert photography on trains are also on the rise, according to official figures. The new trick dubbed 'fishing' emerged last year whereby the thieves, who usually targeted women, get hold of an earphone cord attached to a mobile phone and use it to pull the gadget from an unzipped handbag or a large pocket, often when victims are getting off trains. Of the 85 smartphone pickpocketing cases in the first five months of this year, 29 involved such a technique. Police railway district commander Henry Tam Chak-hang said: 'Listening to music on the MTR is very common, so it is very easy for criminals to locate targets.' He suggested using wireless Bluetooth earphones, or installing anti-theft apps, which trigger a siren when the earpiece is unplugged. Railway police recorded 515 criminal cases in the first five months of this year, 129 of which involved pickpocketing. These most often happened in Kowloon Tong, Central, Causeway Bay, Mong Kok and Tsim Sha Tsui and in most cases those arrested were from the mainland. Indecent assault and covert photography are also on the rise. There were 69 indecent assaults in the first five months of the year, a 28 per cent rise on the same period last year. Some 38 suspects, all men, were arrested. There were 38 cases of concealed photography - which in most cases involved a photograph being taken up a woman's skirt - a 40 per cent rise from first five months of 2011. Some 35 male suspects, aged 13 to 49, were arrested.