A strike called by Pakistan's hardline Islamic parties in response to a week of sectarian violence has been almost fully observed in Karachi.
A student is arrested during unrest in Karachi on Friday
There were sporadic reports of unrest as worshippers attended Friday prayers in the tense southern city.
The strike call in some other parts of the country was less effective.
The killing in Karachi on Sunday of a Sunni Muslim cleric was followed a day later by a bomb attack on a Shia mosque which killed 23 people.
The toll rose to 23 on Thursday when two more people died of their wounds.
Three others were killed in clashes with police that followed the mosque attack.
Friday's strike brought Karachi to a virtual standstill, with shops closed and many streets empty of vehicles.
Thousands of security personnel are on Karachi's streets
The Karachi Stock Exchange closed after the morning session because of thin attendance by investors.
Thousands of security forces were deployed on the streets.
Nevertheless, there were reports of an attack by a mob on a police station in the city in which six civilians and four officers were injured.
A police inspector in the Pirabad area, Dilip Kumar, said tear gas was fired to disperse a crowd of around 150.
The strike call was also well observed in other towns of Sindh province and in Quetta, capital of Balochistan province.
However, in most other parts of the country it was not so well heeded, with only a few scattered protests.
The Islamic opposition parties of the Muttahida Majlis-e-Amal (MMA) alliance staged rallies in various cities, condemning the sectarian violence.
But the MMA reacted coolly to a proposal by the ruling Pakistan Muslim League for a united Sindh provincial government to tackle the sectarian violence.
MMA acting head Qazi Hussain Ahmad said: "The government is not serious about... a coalition in Sindh. No concrete proposal has been put forward."
PAKISTAN'S SECTARIAN DIVIDE
Shia revere Ali, son-in-law of the Prophet Mohammed
Pakistan is 20% Shia, 70% Sunni
Violence between Sunni and Shia factions began in 1980s
Over 150 people have died in the past year alone
Around 4,000 people have been killed in total
Most violence takes place in Sindh, Balochistan and Punjab
The bloodshed in Karachi began on Sunday with the killing of senior Sunni cleric, Mufti Nizamuddin Shamzai, by unidentified gunmen.
A day later the bomb blast at the Shia mosque during evening prayers killed 23, injured about 40 and caused extensive damage to the building.
Police are carrying out DNA checks on a skull found at the scene which is believed to be that of the suicide bomber.
Both events sparked riots by members of the respective communities.
No one has said they carried out either attack.
President Pervez Musharraf quickly pledged action to curb the sectarian violence, but has so far given no details.
On Wednesday, the police chief of Karachi, Asad Malik, and two other township police chiefs were transferred.
Sunni-Shia sectarian violence has killed as many as 4,000 people in the past 15 years in Pakistan.
The BBC's Zaffar Abbas in Islamabad says Karachi in particular has a long history of religious and ethnic violence, but the month of May was the worst in recent years - with more than 50 people killed in different incidents of violence.
Three weeks ago at least 14 people were killed when a man, apparently dressed as a Shia cleric, blew himself up in a Shia mosque.