Filed at 10:54 a.m. ET

LAHORE, Pakistan (Reuters) - Pakistan's main political alliance said Tuesday the military government had arrested more than 1,600 activists in the central province of Punjab to try to prevent an opposition rally Friday.

But the 18-party Alliance for the Restoration of Democracy (ARD) vowed to go ahead with the protest in the Punjab state capital Lahore on a national day despite what it called the unprovoked crackdown that began Monday night.

The government, which banned public rallies in March 2000, was not immediately available for comment on the crackdown, which appeared to be the biggest since military ruler General Pervez Musharraf seized power in an October 1999 army coup.

An ARD official said 1,650 people had been arrested up until 3 p.m. Tuesday.

ARD said its politicians would boycott a discussion on provincial autonomy organized by state television for Tuesday night.

``I have received information from all over the province that the police have arrested hundreds of workers in midnight raids,'' Punjab ARD president Qasim Zia told an earlier news conference.

Political sources said most of the arrested people were members of the Pakistan People's Party (PPP) of self-exiled former prime minister Benazir Bhutto.

PPP deputy secretary-general Raza Rabbani told a news conference in Islamabad that in some cases police arrested politicians' children if their parents were not at home.

DOUBLE STANDARDS SEEN

Rabbani accused the military authorities of applying double standards in dealing with political parties and said it was allowing right-wing and religious groups to holding meetings and display weapons, but was blocking liberal parties from expressing peaceful political dissent.

``If somebody thinks the March 23 public meeting will not be held because of these arrests, he will be wrong,'' Asfandyar Wali, leader of the Awami National Party, told the Islamabad news conference. ``That meeting will be certainly be held.''

The ARD, which also includes the Pakistan Muslim League party of ousted prime minister Nawaz Sharif, had planned the Lahore rally to start a campaign against the 17-month-old military government on what is called Pakistan Day.

The government has arranged military parades to mark the day, which commemorates a resolution passed by the then All India Muslim League party demanding the creation of Pakistan as a separate Muslim homeland from British-ruled India.

The government banned public rallies when President Clinton made a few hours' stopover in Pakistan. It left the ban in place.

The ARD said it would hold the rally regardless.

PPP secretary-general Jehangir Badar told the Lahore news conference that the ARD was holding rally ``after fulfilling all legal requirements.''

He said mass arrests of political workers and leaders to stop the rally was ``not fair play'' but harmful to national solidarity.

Musharraf seized power in October 1999 when he toppled Sharif in any army coup. He released Sharif from prison in December and exiled him to Saudi Arabia for 10 years.