Afghanistan has been hit by a wave of deadly bombings, for which the revitalized Taliban have denied responsibility. Visiting Kabul, Guterres says the UN 'stands with Afghanistan at a time of violence and suffering.'
UN Secretary-General Antonio Guterres landed in Kabul on Wednesday for a surprise visit to Afghanistan.
"Just landed in Kabul for talks with government and people," Guterres said on Twitter.
The UN "stands with Afghanistan at a time of violence and suffering," he said.
More than 180 people have died in Kabul since the beginning of June in a series of bombings. More than 600 others were wounded.
Biggest Kabul attack since 2001
On May 31, a truck bomb near the German Embassy killed more than 150 people, mostly Afghan civilians, and wounded another 460.
Officials were quick to blame the Taliban but the Taliban and the Taliban-allied Haqqani network ruled out any involvement in the wave of Kabul bombings.
"We have already condemned the (attacks). The Islamic Emirate (Taliban) is not behind them," the group's deputy leader Sirajuddin Haqqani said in an audio message posted on the group's website on Sunday.
"The enemy wants to defame Mujahideen and create a distance between the nation and Mujahideen."
Afghanistan is still fighting against the Islamist Taliban movement after they steadily expanded their reach since the US and international forces formally concluded their combat mission at the end of 2014.
An affiliate of the so-called "Islamic State" also emerged and carried out several large attacks in the country.
The conflict helped fuel a migration crisis - a topic which interests Guterres, who headed the UN's refugee portfolio for several years.
About 250,000 Afghans fled for Europe last year, while 800,000 moved within the country.
More than 22,000 people were displaced in the past two weeks alone, data from the UN Office for the Coordination of Humanitarian Affairs showed, with northern and northeastern Afghanistan most affected.
Meanwhile, hundreds of thousands of Afghans returned from neighboring Pakistan as relations between the two countries grew tense.
Potentially more US troops
On Tuesday US President Donald Trump gave Defense Secretary Jim Mattis the authority to set troop levels in Afghanistan, opening the door for future troop increases requested by the US commander, Reuters reported.
An anonymous official told the news agency that no immediate decision had been made about the troop levels, which are now set at about 8,400.
"We are not winning in Afghanistan right now," Mattis said in testimony to the Senate Armed Services Committee earlier on Tuesday. "And we will correct this as soon as possible."
Mattis said the Taliban were "surging" at the moment, something he said he intended to address.
Tour of Central Asia
Guterres had come from the capital of Turkmenistan on Tuesday, where he was urging ex-Soviet Central Asian states to observe human rights in the fight against extremism, as part of a tour of the Muslim-majority region.
Guterres said that "policies that limit human rights only end up alienating religious and ethnic communities, who would normally have every interest in fighting extremism."
Guterres also thanked the countries for their "commitment to jointly addressing and defeating the scourge of terrorism."
Central Asia's secular authoritarian governments had cracked down hard on religious groups operating outside state control amid concerns over the potential spread of religious extremism in a region closely tied to Russia and China.
The UN secretary-general's visit to the region began on June 8 in Kazakhstan, where he attended a meeting of the Russia and China-led Shanghai Cooperation Organization before visiting Kyrgyzstan on Sunday.