ISLAMABAD (AP/AFP) - Pakistan's prime minister says he has warned the international community that India could launch an attack on Pakistani-held Kashmir to divert the attention from human rights abuses in its portion of the disputed Himalayan region.

In a speech at a rally in Islamabad, Imran Khan says his country will give a "befitting response" to the government of Indian Prime Minister Narendra Modi if it attacks Pakistan.

He described Modi as a "fascist" and equated him with Adolf Hitler, saying he fears a "genocide of Muslims in Kashmir".

"We will stand with Kashmir until our last breath," said Khan, while launching into a blistering attack on Indian Prime Minister Narendra Modi and comparing his administration to the Third Reich in Nazi Germany.

Rallies were held across Pakistan on Friday (Aug 30). Thousands rallied in mass demonstrations protesting Delhi's actions in Indian-administered Kashmir in the most ambitious public protests targeting India in years.

At noon, sirens rang out across the country followed by broadcasts of the national anthems of Pakistan and Kashmir, while traffic ground to a halt for several minutes in solidarity with the rallies.

In the capital Islamabad, thousands gathered on Constitution Avenue in front of the government offices where Khan addressed the nation and vowed to continue fighting for Kashmir until the disputed Himalayan territory was "liberated".

The demonstration was the first in what will be weekly rallies held nationwide until Khan leaves for New York next month to attend the United Nations General Assembly, where he vowed to raise the Kashmir issue.

Tensions between Pakistan and India have increased since Aug 5, when New Delhi downgraded Kashmir's autonomy.

The area is currently in its fourth week of a wide-ranging communications blackout with severe restrictions on movement. Thousands of people have been incarcerated in the crackdown, sources have told AFP.

In the weeks since the move, Khan has launched a wide-ranging diplomatic offensive to counter Delhi, while vowing to fight India "until the end" if attacked and making occasional references to the possible outbreak of nuclear conflict.

Kashmir has been divided between the two countries since independence, and has been the spark for two major wars and countless clashes between the arch-rivals. In February, the rivals again came close to all-out war, after a militant attack in Indian-held Kashmir was claimed by a group based in Pakistan, igniting tit-for-tat air strikes - the first between nuclear-armed nations.

The protests in Pakistan came a day after its military announced the testing of a surface-to-surface ballistic missile, with the army's spokesman saying the weapon was "capable of delivering multiple types of warheads".

India on Thursday said it has information that Pakistan is trying to infiltrate "terrorists" into the country.