* Protesters demand end to Bani Walid violence
* Militiamen have shelled Bani Walid for several days
* Many militia fighters are from rival town Misrata
* Conflicting reports over fate of Gaddafi spokesman, son (Adds Benghazi TV station incident)
By Ali Shuaib
TRIPOLI, Oct 21 (Reuters) - About 500 protesters broke into the grounds of Libya's parliament building on Sunday to demand an end to violence in Bani Walid, a former stronghold of the late Muammar Gaddafi that is being shelled by militiamen from a rival town.
Militias, many from Misrata and aligned with the Defence Ministry, have been shelling the hilltop town of 70,000 people for several days. State news agency LANA said on Sunday that 22 people had been killed and 200 wounded in the fighting.
"We are here to demand the government find a peaceful solution for the tribal war that is happening in Bani Walid," protester Nasser Ehdein said.
Libya's new rulers have held elections but have struggled to impose their authority on a country awash with weapons a year after Gaddafi was killed and the fighting in Bani Walid underscored how tenuous their control remains.
In a country where rumours abound, there were also conflicting reports over the weekend about the fate of Gaddafi's son Khamis and that of the late autocrat's former spokesman.
In Tripoli, an unarmed group of male and female protesters forced their way past security guards at the gates of the grounds of the parliament buildings, chanting "There is no God but God, and President (Mohammed) Magarief is God's enemy."
Security forces fired rounds into the air as they held their positions at the doors of the building, while elected members of the General National Congress met inside.
Ehdein said most of the protesters were residents of Tripoli who had family in or hailed from Bani Walid.
This is the second time protesters have broken into the grounds of the assembly since it took power in the summer.
The first time was on Oct. 4 when a group of protesters who believed their town was underrepresented in a proposed Libyan government stormed the assembly as it prepared to scrutinise the prime minister-elect's nominations.
In the port city of Benghazi anger boiled over on Sunday night where about 400 unarmed but angry protesters stormed the grounds of private Libyan satellite channel Libya al-Ahrar.
The protesters demanded that the channel air photographic evidence that Gaddafi's son Khamis had been killed in battle. Libyan officials had announced he had been killed in fighting in Bani Walid but that has not been confirmed.
Demonstrators said they were furious over what they deemed a false rumour, saying it had helped fuel violence in Bani Walid and stir up tribal enmity.
Bani Walid was one of the towns that remained loyal to Gaddafi the longest. It remains isolated from the rest of Libya and former rebels say there are still pockets of support for the old government there.
In Bani Walid itself, 140 km (86 miles) south of Tripoli, militia leader Abdelkarim Ghomaid said fighting was in full swing.
"The shelling is coming from all sides," he said by phone.
A Bani Walid resident said by phone: "Fighting is continuing today. There is smoke rising over certain parts of the city."
Outside Bani Walid, hundreds of vehicles lined up in the village of Weshtata, 80 km (50 miles) from Tripoli, waiting to be checked by government forces as families fled the fighting.
"We are escaping the danger of the rockets, the shrapnel, and the deaths inside. There hasn't been electricity for days," said one man who had his family in a pick-up truck.
A feud between Misrata and Bani Walid was inflamed by the death of rebel Omran Shaban after he was detained for two months in Bani Walid. Shaban, from Misrata, was the man who found Gaddafi hiding in a drain pipe in Sirte on Oct. 20, 2011.
Libya's congress ordered the Defence and Interior Ministries to find those responsible for abducting Shaban and suspected of torturing him. It gave Bani Walid a deadline to hand them over.
Hundreds of families have fled the fighting in Bani Walid to Tarhouna, some 80 km away, where a statement from the prime minister's office on Saturday said militias had captured former Gaddafi spokesman Moussa Ibrahim.
However, in an audio clip posted on Facebook, a person purporting to be Ibrahim, who held news conferences in Tripoli during the war, dismissed news of his arrest.
There was no independent verification of the authenticity or timing of the Facebook post, dated Oct. 20.
Some officials said Gaddafi's son Khamis had been captured in Bani Walid and died after being taken to Misrata. But there was no official written statement from the government on this, as with previous captures of former Gaddafi-era figures.
On Sunday, Deputy Prime Minister Mustafa Abushagur said on his official Twitter account that the announcement of Ibrahim's arrest and Khamis's death was made without confirmation of the news.
Khamis was reported dead on at least three separate occasions during last year's conflict. A Syrian-based television station that supported Gaddafi said he had been killed in fighting southeast of Tripoli on Aug. 29, 2011. (Additional reporting by Hadeel al-Shalchi, Marie-Louise Gumuchian and Reuters Television; Editing by Alison Williams and Andrew Osborn)