During the massive anti-regime demonstrations held on Sunday, the protesters called on the Bahraini regime to immediately release political prisoners in the Arab country.

The protests were held in different regions of the tiny island country, including Musalla on the western outskirts of the capital city, Manama, and Ma'ameer in northern Bahrain, according to Al Alam news website.

It came as Bahrain's main opposition group al-Wefaq has raised the alarm over the plight of more than 1300 inmates being held in the country's notorious Jaw prison.

The opposition group has reported that the prisoners are beaten by guards and are banned from family visits and even phone calls.

Al-Wefaq has called on the International Red Cross to take action to protect the Bahraini inmates.

The Western-allied kingdom, which is home to the US Navy's 5th Fleet, has been witnessing almost daily protests against the ruling Al Khalifa dynasty since early 2011, with Manama using heavy-handed measures in an attempt to crush the demonstrations.

Scores of Bahrainis have been killed and hundreds of others injured and arrested in the ongoing crackdown on the peaceful demonstrations.