Lucknow, Dec 6 (IANS): Authorities have stepped up security across Uttar Pradesh on the 25th anniversary of the demolition of the Babri Masjid at Ayodhya.

Twenty-seven additional companies of the Provincial Armed Constabulary (PAC) have been posted all over the state.

Of these, six companies each have been deployed in Lucknow and in Faizabad district, which includes the temple town of Ayodhya.

Ayodhya has been divided into four zones and 10 sectors and prohibitory orders have been issued banning the assembly of four or more people.

Mobs allied to the Vishwa Hindu Parishad (VHP) tore down the 16th century Babri Masjid in Ayodhya on December 6, 1992, triggering widespread communal riots all over the country.

While the VHP -- which claims the Babri Masjid was built at the birthplace of Hindu god Rama -- has been celebrating the demolition as 'Shaurya Diwas', some Muslim groups observe December 6 as a "black day".

All firecracker shops have been asked to shut down, officials said. Police been asked to arm themselves with riot gear as well as rubber bullet guns.