The arrests, and the placing of a radical Islamist leader under house arrest, came amid fears of renewed violence across the country.
Police have been ordered to restrict the movement of all religious leaders who might address rallies and round up religious activists "who could be any threat to law and order," a senior police official said in the main eastern city of Lahore.
In Multan, another city in Punjab province, about 300 policemen swooped down on 125 protesters, who gathered on Friday morning at a traffic circle, chanting, "We are slaves of the prophet," and trampling on a Danish flag, said Sharif Zafar, a police official.
Protesters shouted "Death to Musharraf" as they were bundled into two police buses, referring to General Pervez Musharraf, Pakistan’s president.
Zafar said they were being taken to a police station, because they were violating a ban on rallies in Punjab - declared after deadly riots in Lahore on Tuesday.
In Karachi, police fired tear gas and swung batons to disperse about 2000 protesters, many wielding sticks, who blocked the main highway into the southern city, Alim Jafari, a Karachi police official, said.
The road was cleared and some 30 protesters were detained, he added.
Challenge to Musharraf
Protests in Pakistan against the cartoons turned violent this week. Five people have died in riots, and Western businesses have been vandalized and burned.
The violence may undermine the
Musharraf government's authority
The cartoons first appeared in a Danish newspaper in September and have since been condemned as blasphemous by the Muslim world. One of the drawings shows Muhammad wearing a bomb-shaped turban with an ignited fuse.
A spokesman for the radical group Jamaat al-Dawat said a heavy contingent of police arrived at the Lahore home of its leader, Hafiz Mohammed Saeed, on Friday morning and told him he could not go outside. He was due to make a speech in Faisalabad, about 120km (75 miles) away, said Yahya Mujahid, the group’s spokesman.
The police official confirmed Saeed had been confined at his home. Saeed used to lead Lashkar-e-Tayyaba, a militant group closely associated with Jamaat al-Dawat, and was banned by Musharraf four years ago.
Intelligence officials have said scores of members of Jamaat al-Dawat and assorted militant groups joined the Lahore protest on Tuesday and had incited the violence in a bid to undermine the authority of Musharraf's government.
Khawaja Khalid Farooq, the Lahore police chief, aid 12,000 policemen and an unspecified number of paramilitary troops were guarding government and foreign installations, mosques and other public places like shopping centres, restaurants, cinemas and bus stops.
Police and soldiers are guarding
major buildings and installations
“There is a ban on rallies and we will not allow any one to violate the ban,” he said.
In Karachi, a youth group called Pasban called a strike in the teeming port city on Friday, where about 40,000 people had joined a peaceful protest the previous day.
“We expect that people of all sects and walks of life will keep their businesses shut to convey a message to the Western world,” said Altaf Shakoor, Pasban's chief.
Supporters of the radical Jamaat-e-Islami, Pakistan's largest Islamic group, also planned to hold rallies in Karachi after midday prayers on Friday, said Sarfaraz Ahmed, a spokesman for the anti-US group.
Niaz Ahmed Siddiqi, the Karachi police chief, said police and paramilitary troops were patrolling the streets, and all foreign missions and foreign food chains were heavily guarded.
More anti-cartoon protests were expected on Friday in other Pakistani cities, including Rawalpindi, Quetta and Peshawar - the northwestern city ravaged by riots on Wednesday.
Police were guarding multinational businesses and government buildings, witnesses said.