ISLAMABAD, Feb 2: Opposition parties made fresh vows on Wednesday to struggle 'against sweeping presidential powers' as they inaugurated their new leader in the Senate before a bitter start of a debate on unrest in Balochistan.

Senators from both the treasury and opposition benches showered tribute on Democratic Alliance and PPP parliamentary leader Raza Rabbani on his belated notification as opposition leader in the 100-seat upper house.

Shortly after assuming his new role, Mr Rabbani led a token opposition walkout to protest against General Pervez Musharraf's decision to keep with him both the presidency and the office of the army chief until 2007 and the latest increases in petroleum prices.

In his speech, Mr Rabbani promised to carry along all opposition groups, including the Muttahida Majlis-i-Amal (MMA) that had made a rival claim to the office of opposition leader, in a struggle to undo 'the controversial 17th constitutional amendment made more than a year ago to give parliamentary approval to sweeping powers President Musharraf had assumed through a Legal Framework Order (LFO).

"Our struggle will continue until we are able to scrap it," he said of the amendment. "We are also against the double office (held by the president) and will carry on our struggle until victory," Mr Rabbani said.

MMA parliamentary stalwart Prof Khurshid Ahmed said a 'social contract' between his alliance of six Islamic parties and the government - he also called it a 'national covenant' - about the 17th amendment was no longer valid because of its alleged violation by the president.

He said General Musharraf was only de facto president but the de jure position was that he was illegally holding both offices, for which he was empowered by a separate act passed by parliament.

On a motion moved by Mr Rabbani, the house unanimously agreed to discuss the Balochistan situation in light of recent acts of violence, but the debate had an acrimonious start with strongly-worded speeches from opposition Senators from the troubled province.

Senator Amanullah Kanrani of the Jamhoori Watan Party called the alleged rape of a lady doctor at the Sui gas field, which triggered the recent violence, as part of a conspiracy by those opposing still unannounced recommendations of a parliamentary committee on Balochistan.

He said a four-party alliance of Baloch nationalist parties would no longer accept the parliamentary committee until an army officer accused of raping the doctor was arrested and troops and tanks deployed in Sui area were withdrawn.

Mr Kanrani described the military deployment in the area as "a declaration of war against Balochistan" that he said the Baloch people would resist. Tensions rose as PML senator Kamil Ali Agha recalled an old incident in Lahore allegedly involving a son of Mr Akbar Bugti to which an ally of the ruling coalition, Mohim Khan Baloch of the Balochistan National Party (Awami), and Mr Raza Rabbani objected.

PML's Senator Khalid Ranjah, a former law minister, counselled patience and asked both sides of the house to consider the real issue of the quantum of provincial autonomy required for the provinces by possible curtailment of the present concurrent list of the constitution.

Senator Raza Mohammad Raza of the Pukhtunkhawa Milli Awami Party also made a strongly worded tirade against what he called policies to usurp resources of the smaller provinces and said: "Balochistan now in a state of war".

"You are forcing people there to use other means," he said of the perceived resentment in Balochistan. Leader of the house, Wasim Sajjad, took a strong objection to these remarks and said all four provinces of the country would remain together and "Pakistan will never disintegrate".

From the treasury benches, Parliamentary Affairs Minister Sher Afgan Khan Niazi, prime minister's Adviser on Women Development Neelofar Bakhtiar and Senator Mrs Tanvir Khalid all said those responsible for the lady doctor's rape at Sui deserved exemplary punishment but advised the opposition not to exploit the incident for other purposes or justify violence and attacks on national assets.