About 3000 supporters of Jamaat-e-Islami, Pakistan's largest Islamic group, rallied in Islamabad, Pakistan's capital, on Sunday chanting "Allahu Akbar", or "God is great".
About 400 other Jamaat-e-Islami supporters demonstrated on a main street in Muzaffarabad, the capital of Pakistani-administered Kashmir.
The rallies marked "Kashmir Solidarity Day", when Pakistanis show support for Kashmir's independence from India.
Most shops in Muzaffarabad were closed and General Musharraf, the Pakistani President, was to address a gathering in the city later on Sunday.
In a message on the eve of the solidarity day, Musharraf said it commemorated the sacrifices of Kashmiris who had died fighting for independence from India, state-run Associated Press of Pakistan news agency reported.
Pakistan and India control separate parts of Kashmir, but both claim the entire region.
About a dozen hardline Muslim groups have been fighting in Indian-controlled Kashmir, demanding either independence or a merger with Pakistan.
About 67,000 people, mostly civilians, have been killed since the insurgency began in 1989.
India accuses Pakistan of backing the separatists, but Islamabad denies the accusation, saying it only gives moral, political and diplomatic support to the Kashmiris' "freedom struggle".
"He (Pervez Musharraf) has forgotten Kashmiris and they have been left alone"
Syed Munawar Hassan,
Pakistan and India have fought two wars over Kashmir since their independence from British rule in 1947.
Two years ago the two countries began a series of negotiations directed at settling Kashmir and other disputes.
The countries have since restored travel links and eased travel restrictions between them, but have made little headway on Kashmir.
At the rally in Islamabad, a senior Jamaat-e-Islami leader rejected the negotiations over Kashmir, saying Musharraf had turned his back on Kashmiris by becoming friends with India.
"He has forgotten Kashmiris and they have been left alone," Syed Munawar Hassan said to the chanting crowd.