Judge who refused to swear oath is Musharraf's rival in elections

General Pervez Musharraf has formally submitted his nomination papers ahead of next week's presidential election – setting himself up for another showdown with the country's newly resurgent legal community.

With Islamabad under lock-down, Prime Minister Shaukat Aziz went to the election commission to file the general's documents. Another 42 candidates also submitted their candidacies, including former Supreme Court judge Wajihuddin Ahmed, who has emerged as a challenger to General Musharraf, representing liberals. With the nomination of Mr Ahmed – a 68-year-old noted for his tinted glasses, leather jackets and cowboy boots who resigned in 2000 after refusing to pledge an oath of allegiance to General Musharraf – the legal community is seeking to open up another front in its attempt to dislodge the president. The Supreme Court has this week heard a series of constitutional challenges to General Musharraf's candidacy and is expected to rule today.

Last night the court's chief justice, Iftikhar Chaudhry, ordered the release of more than 200 opposition members who have been rounded up in on the president's orders. He also summoned police and government officials to explain who had ordered the closure of all the roads leading into the nation's capital yesterday in an apparently transparent attempt to halt a demonstration by lawyers against General Musharraf's candidacy. In Lahore, around 1,000 lawyers held a separate demonstration.

General Musharraf – who has seen his popularity fall since the spring – has gambled on holding the election next weekend as his best way of securing another five years in office. Opposition figures have argued that the national and regional assemblies that elect the president should themselves hold elections, as their own terms are set to expireand the politicians have no mandate to select a head of state for the next five years.

What seems clear is that former prime minister Benazir Bhutto does not intend to interfere with General Musharraf's election plans. Unlike another former premier, Nawaz Sharif, whose attempt to return to Pakistan to challenge the general was foiled by the regime earlier this month, Mrs Bhutto appears to have come to an arrangement with the military leader – whether explicit or not – that he will remain as president yet allow her to again become prime minister following parliamentary elections, next January.

To that end Mrs Bhutto's party, the Pakistan People's Party (PPP) also nominated a candidate for the presidency but made clear that Makhdoom Amin Fahim, the party's vice-chairman, would only stand if General Musharraf was barred from standing by the court.

The Supreme Court has to decide whether the constitution bans military officers from seeking political office, as the lawyers seeking to block General Musharraf have argued.

General Musharraf, who seized power in a 1999 coup, has pledged to step down as military chief and restore civilian rule if he gets a fresh mandate. But his lawyers have also said he would remain as head of the armed forces if he is not re-elected next Saturday. This has led to claims from some opposition figures that General Musharraf will announce a state of emergency.