A mobile phone was linked by wires to both launchers, apparently as a remote triggering device for the Russian-made rockets, security officials said on condition of anonymity.

"These two rockets were not target-specific," Sherpao said, adding that the placing of the rockets "appears to be aimed at creating chaos and confusion in the capital and harassing the general public."

"It could also be an attempt to undermine the successful visit of President General Pervez Musharraf to the EU headquarters in Belgium, Cuba, United States and United Kingdom."

But a security official said the rockets were "apparently pointing towards the presidency."

"Luckily some labourers working at a construction site saw the rockets and reported it to police," the official said.

Police cordoned off the area and security forces detained 80 people working at the site for questioning, officials said.

The fact that the 107 mm calibre rockets were made in Russia indicated they had come via Afghanistan, which borders on ex-Soviet Central Asia, and possibly implicates extremist Taliban rebels, security sources said.

Later Musharraf arrived by helicopter at an Islamabad conference hall to give a speech -- shortly after three heavily guarded but empty motorcades had driven up in an apparent decoy security measure.

Musharraf, who has survived at least four previous assassination attempts, did not comment on the rocket find.

The rockets were discovered about 12 hours after an explosion in a public park near General Musharraf's army residence in the garrison city of Rawalpindi, which adjoins Islamabad, late Wednesday.

Chief military spokesman Major General Shaukat Sultan told AFP the blast "had nothing to do with the president or army house".

Sultan, who is also Musharraf's press secretary, said some explosive material was found at the blast site and that police were investigating. Police said they sent another bomb disposal team and search parties to the site.

One security official earlier told AFP that the blast in Ayub Park was caused by a rocket but senior authorities later denied this. Officials also rejected reports that a large quantity of unexploded material was found.

Musharraf, a key ally in the US "war on terror", seized power in a bloodless coup in 1999 and has survived two assassination attempts in Rawalpindi, both in December 2003.

In the first, suspected Islamic militants blew up a bridge as his motorcade passed but Musharraf was saved when electronic jamming equipment in his car delayed the blast.

The second attempt on Christmas Day was a suicide attack linked to Osama bin Laden's al-Qaeda network that left 14 people dead.

In 2004 Pakistani authorities said they had busted a plot to fire rockets at Musharraf from the hills overlooking Islamabad during a national day parade.

Musharraf has blamed the attempts on Islamic militants, who are infuriated by his anti-extremist drives and for abandoning Afghanistan's Taliban after the September 11, 2001 attacks on the United States.

He is also hated by tribal insurgents in southwestern Baluchistan province.

"Musharraf is not short of enemies," said a Western diplomat.