Tribal fighters in Yemen have taken over government buildings in the capital, Sanaa, including the headquarters of the ruling party, sources tell Al Jazeera.
Fighters were also said to be surrounding the building of the interior ministry, Aljazeera correspondents reported on Tuesday.
"[The buildings are] very close to the house of the [Hashed] tribal leader [Sadiq al-Ahmar] that was almost damaged by the shelling of the last few days," Mohamed al-Qadhi, the correspondent for the Abu Dhabi newspaper The National, told Al Jazeera.
"People of the tribal leader have said they control it but we are getting reports that it was taken by another military brigade, and they said they will prevent fighters from attacking the house of al-Ahmar from this building."
At least 320 people have been killed in fighting in Yemen since protests calling for Ali Abdullah Saleh, the president, to end his 33-year rule started about four months ago, inspired by the popular uprisings that ended the reign of the long-standing rulers of Tunisia and Egypt.
Street clashes
On the second day of continuing street clashes between Saleh's security forces and Hashed tribesmen, hundreds of explosions were heard, several people killed and dozens injured in Sanaa on Tuesday.
The most intense fighting was in the Hasaba district, close to al-Ahmar's residence.
"There have been heavy clashes and confrontations. It is the most severe and the most clashes that have taken place in Sanaa since the two sides started clashing with one another," al-Qadhi, the Sanaa-based journalist, said.
"The tribal leader's supporters are concerned more with the places used to launch attacks on al-Ahmar and his supporters. So I think they are expanding their control over several government buildings."
A tenuous truce declared a few days ago to end street fighting between the two groups broke down, with a government official on Tuesday saying "the ceasefire agreement has ended".
In another incident, security forces reportedly shot dead at least two anti-government protesters in Yemen's second-largest city, Taiz, on Tuesday, witnesses said.
They said that security forces were attempting to prevent anyone from gathering in the city, firing on those who tried to do so.
Medics confirmed that at least two people had been killed.
Flashpoint cities
Tuesday's deaths came after protesters said security forces smashed a four-month-long sit-in in Taiz on Monday, killing 21 protesters.
According to reports received by the UN, more than 50 protesters have been killed in Taiz since Sunday.
"The UN human rights office has received reports, which remain to be fully verified, that more than 50 people have been killed since Sunday in Taiz by Yemeni Army, Republican Guards and other government-affiliated elements," Navi Pillay, the UN human rights chief, said on Monday.
The violence in Sanaa and Taiz follows the killing of at least 30 people in air raids in the southern city of Zinjibar.
PHOTO CAPTION
Yemeni anti-regime activists block a main road in the flashpoint city of Taez, south of Sanaa, with burning tires during a protest against President Ali Abdullah Saleh on June 1, 2011.
Al-Jazeera