Clashes between protesters and security forces left dozens of people injured in Libya today, as the upheavals which led to the overthrow of regimes in Tunisia and Egypt continued to spread across the region.

In Benghazi, Libya's second largest city, demonstrators chanting "Allah il Allah" and "Allah shall triumph over unbelievers" threw petrol bombs and set cars alight in a sign of the increasingly religious fervour of the rare marches against the regime of Colonel Muammar Gaddafi, the Arab world's longest-serving leader.

The rallies followed the arrest of a human rights campaigner, Fethi Tarbel, which acted as a trigger for opposition groups to take to the streets.

The authorities appeared to have been taken by surprise at the rapid escalation of the unrest, while groups of young people used Facebook to try to organise a "day of rage" for today.

The violence overnight in Benghazi, 600 miles east of the capital, Tripoli, left around 40 people injured, said Abdelkarim Gubaili, director of the city's General Hospital. Most of them were members of the security forces, he said, who were unprepared for the level of violence they had faced.

Around 600 demonstrators had marched to the local government headquarters in Sabri district and attempted to get inside the building. Scuffles turned to running battles when security forces attempted to intervene.

Residents said a semblance of normality had returned to the city by yesterday afternoon. Shops, businesses and some bank branches reopened. Fazal al-Manisi, who had shut down his furniture business, said "we had a night of bad trouble. They were shouting, saying Allah is against corruption and all those responsible should be in prison".

In an effort to counter the protests, Libyan television yesterday showed footage of pro-government rallies in Tripoli and Benghazi with supporters holding portraits of Colonel Gaddafi and chanting: "We sacrifice our blood and souls for you, our leader." The regime also released 110 prisoners belonging to the banned Libyan Islamic Fighting Group. It was the largest release in recent times by the regime, which had carried out a ruthless campaign against fundamentalist groups in the country.

"What is happening in Libya is very significant," said Ali Mohammed Ben- Nayim, an analyst of North African politics based in London. "This is an authoritarian state which does not allow dissent, but that is what they are facing. No amount of pro-Gaddafi marches can stop what is happening in the Arab world."

Elsewhere, the tiny gulf state of Bahrain was hit by a third day of protests as thousands gathered for the funeral of a demonstrator killed by the security forces.

And police in Yemen flooded the streets to try to quell nearly a week of anti-government unrest, sparking fresh clashes that left one protester dead.

In the country's southern port town of Aden, about 500 people turned on police who had tried to disperse the crowd by firing in the air and deploying tear gas. Yemen has been gripped by six days of protests against the President of 32 years.