United Nations Secretary General Ban Ki-moon arrived in Islamabad on Wednesday afternoon after a brief stop in Kabul where he held talks with Afghan leaders, reported dpa.
During his first visit since taking office in late 2006, Ban is expected to meet Pakistani Prime Minister Yousuf Raza Gilani and President Asif Ali Zardari, an official of Pakistan's foreign ministry said.
The visit came two days after unknown gunmen kidnapped a senior UN official in north-west Pakistan.
"This issue will definitely come under discussion and Mr Ban will ask Pakistan to ensure the safe release of abducted UN official," said the Pakistani official.
John Solecki, the head of the UN refugee agency was kidnapped in the south-western town of Quetta as he was going to his office on Monday. The attackers killed his Pakistani driver.
Police were investigating but it was not clear who was responsible for the abduction in Quetta, which is believed to be a hotbed of al-Qaeda and Taliban militants. The city is also facing a homegrown insurgency by Baloch separatists.
Ban was also scheduled to discuss the formation of a UN commission to probe the assassination of former prime minister Benazir Bhutto with the Pakistani leadership, including her widower Zardari.
Bhutto was murdered in a suicide attack on December 27, 2007 during an election rally in the garrison town of Rawalpindi.
A Taliban commander named Baitullah Mehsud was initially blamed for the slaying, but he denied the allegations.
The government asked the UN last year to set up a commission to investigate the assassination.
"Pakistani leaders will also have opportunity to exchange views on regional and international security situation," said the foreign ministry official.
Earlier, Ban held talks with Afghan President Hamid Karzai and leaders of the national assembly during his surprise visit to Kabul.