A march by hundreds of supporters to demand the release of jailed former Prime Minister Imran Khan reached the fringes of Pakistan's capital of Islamabad on Monday, his party and officials said, amid reports of violence elsewhere.
Authorities have enforced a security lockdown for the last two days to block the protesters, whom Khan has called on to march on parliament for a sit-in demonstration, while highways into the city have been barricaded.
The government has used shipping containers to block major roads and streets in Islamabad, most of them patrolled by large contingents of police and paramilitary personnel in riot gear.
Officials and witnesses said all public transport between cities and terminals has also been shut down in the eastern province of Punjab to keep away the protesters, led by members of Khan's Pakistan Tehreek-e-Insaf (PTI) party.
"We wouldn't let them storm the capital," said provincial Information Minister Uzma Bukhari, adding that about 80 of Khan's supporters had been arrested.
Several police officials were injured in clashes and rioting at some places in the province, she told a news conference.
The capital added an extra layer of security ahead of a visit by the president of Belarus, Aleksandr Lukashenko, set to
arrive on Monday.
Khan's party accused the government of using violent tactics to block the protesters, saying it had arrested hundreds of workers and leaders.
"They are even firing live bullets," one of Khan's aides, Shaukat Yousafzai, told broadcaster Geo News TV.
Gatherings of any sort in Islamabad have been banned, police said in a statement. Authorities closed all schools in Islamabad and the adjacent garrison city of Rawalpindi, while the internet and WhatsApp messaging services also slowed.
The protest march, which Khan has described as the "final call", is one of many his party had held to seek his release since he was jailed in August last year. The party's most recent protest in Islamabad, early in October, turned violent.

Search expands after Philippine ferry fire kills five and leaves dozens missing
US military says it struck vessel in Caribbean, killing 3
At least 14 killed in explosion at weapons depot in Syria
US hits five Iranian oil tankers after attack on Navy ships
UK gives air traffic provider a week to probe outage that halted flights
Serbia's President Vucic dissolves parliament, calls snap elections
With large crowds attending, Norway lays King Harald to rest
Jordan intercepts 18 Iranian ballistic missiles
