SAN FRANCISCO • Fiat Chrysler said on Wednesday it is offering a software patch for some of its Web-connected vehicles after a report detailed how hackers seized control of a moving 2014 Jeep Cherokee.

The firm said it had no first-hand knowledge of any of its vehicles being hacked. In a statement, it said software updates are sometimes needed "for improved security protection to reduce the potential risk of unauthorised and unlawful access to vehicle systems".

In a story in Wired on Monday, journalist Andy Greenberg described how hackers Charlie Miller and Chris Valasek remotely commandeered the Jeep in an arranged demonstration of a vulnerability, taking over its steering and brakes.

Fiat Chrysler released free software updates for computerised UConnect systems in Chrysler, Dodge, Jeep and Ram models made in 2013 and last year, and some versions of the 2015 Chrysler 200.

A UConnect site on Wednesday featured a box where people could enter vehicle ID numbers to see if they need the updates. The systems handle entertainment, phone, navigation, voice commands and controls, said the site.

As vehicles become rolling smartphones, they open themselves up to viral and criminal threats. A since-closed flaw disclosed in January would have let hackers open doors on 2.2 million BMW AG cars. The programmers who took over the Jeep listed vulnerabilities last year in 19 other models.

AGENCE FRANCE-PRESSE, BLOOMBERG