KABUL (REUTERS, AFP) - Residents of the Afghan capital Kabul reacted with anger and despair on Sunday (Jan 28), a day after a suicide bomb killed and wounded more than 250 people in the worst attack seen in the Afghan capital in months.

The president's office declared Sunday a day of mourning and said Monday would be a day off to allow care of the victims' families.

Across the capital, there was a mix of helpless anger at the seemingly endless wave of attacks after an ambulance packed with explosives blew up in a crowded city street, with security officials warning that more attacks were possible.

"How are we to live? Where should we go?" asked shopkeeper Mohammad Hanif, who was in his shop near the site of the explosion when it went off. "We have no security, we don't have no proper government, what should we do?"

At least 95 people were killed and 158 wounded in the blast, claimed by the Taliban, a week after their deadly attack on the city's Intercontinental Hotel, in a calculated answer to US President Donald Trump's new strategy in Afghanistan.

"The Islamic Emirate has a clear message for Trump and his hand kissers that if you go ahead with a policy of aggression and speak from the barrel of a gun, don't expect Afghans to grow flowers in response," Taliban spokesman Zabihullah Mujahid said in a statement, using the term the use to describe themselves.

Trump urged "decisive action" against the Taliban as other international leaders also condemned the attack.

Trump, who last year sent more American troops to Afghanistan and ordered an increase in air strikes and other assistance to Afghan forces, said the attack "renews our resolve and that of our Afghan partners".

The attack was the worst in the Afghan capital since a truck bomb near the German embassy killed 150 people in May.

Ordinary Afghans took to social media to express their anguish and sorrow at rapidly worsening security, as the Taliban and the Islamic State in Iraq and Syria militant group step up attacks on Kabul, turning it into one of the deadliest places in Afghanistan for civilians.

"We are so heartbroken in Kabul that we don't know how to start our new day," Freshta Karim wrote on Twitter.

"Shall we stay home or go to work, shall we meet our friends and cry or shall we force ourselves to create an illusion of hope? How are you starting your day in Kabul?" Naser Danesh tweeted: "In Kabul starting a day without explosion, it would be a surprise. One could only imagine that kind of a day."

On Facebook Naweed Qaderi wrote: "It is a big shame for the government, they repeatedly fail to protect people. The leaders must lose a son or daughter to feel the pain of poor people."

The blast happened in a crowded area of the city where several high-profile organisations including the European Union have offices.

The force of the explosion shook windows of buildings hundreds of metres away and caused some low-rise structures in the immediate vicinity to collapse.

The government has blamed the Taliban-affiliated Haqqani Network, which Afghan and Western officials suspect of involvement in at least some of the recent attacks in the capital.

Despite a major tightening in checks following the May 31 attack, the ambulance was able to get through the checkpoints, apparently without difficulty.

The suicide bomber passed through at least one checkpoint in the ambulance, saying he was taking a patient to Jamuriate hospital, an interior ministry spokesman told Agence France-Presse (AFP) on Saturday.

"At the second checkpoint he was recognised and blew (up) his explosive-laden car," Nasrat Rahimi said.

Rahimi told a news conference later that most of the victims were civilians. Four suspects had been arrested.

The attack came exactly a week after Taliban insurgents stormed Kabul's landmark Intercontinental hotel and killed at least 25 people, the majority foreigners.

President Ashraf Ghani's Western-backed government has faced growing pressure to improve security and the economy. Last week, militants also carried out a deadly attack on an office of the aid group Save the Children in the eastern city of Jalalabad.

"People don't have work. There's no life for people in Afghanistan. People have to look for a life somewhere else, there's nowhere," said shopkeeper Sameem.

Pressure is likely to mount on Ghani to resolve political confrontation with his opponents, in particular with provincial powerbrokers defying central rule, and focus on security.

"People think the government is working very badly and security is no good," said Najib Mahmood, political science professor at Kabul University.

"The government can control the situation but the president has to share power with others, he needs unity with other parties so they can fight the Taliban together," Mahmood told Reuters.

Former US ambassador to Afghanistan Zalmay Khalilzad called for Ghani's government and its main political rival, powerful northern leader Atta Mohammad Noor, to "come together and resolve their differences".

"Fighting terrorism and protecting the people is job one. I hope they rise to the occasion," Khalilzad said on Twitter.

Saturday's attack drew universal condemnation from neighbouring countries and allies who had expressed confidence that the new US strategy is producing results.

Following a recent visit to Kabul, the US ambassador to the United Nations, Nikki Haley, said the strategy was working and pushing the insurgents closer to peace talks.

However, the Taliban have dismissed any suggestion that they have been weakened by the US approach and say they will only agree to talks when international forces leave Afghanistan.

The United States, which has accused Pakistan of giving assistance to the Taliban and has cut off some aid, urged all countries to take "decisive action" to stop the violence.

Pakistan, which denies the US accusations, condemned the attack and called for "concerted efforts and effective cooperation ... to eradicate the scourge of terrorism".

The president's office also said Joko Widodo, president of Indonesia, which has the world's biggest Muslim population, was due to visit Kabul on Monday. Widodo has proposed that Indonesian Islamic scholars could help promote Afghan peace, media reported recently.