KABUL (AFP) - Explosions rang out in central Kabul on Saturday night, shortly after the US Secretary of State John Kerry left the Afghan capital following an unannounced visit to call for the Taleban to re-enter peace talks.

AFP journalists heard at least two explosions, minutes after the top American envoy's plane departed from the city.

"A rocket landed near a girls' school. There are no casualties," Kabul police chief Abdul Rahman Rahimi told AFP.

No groups have claimed responsibility for the assault, however, Taleban insurgents frequently attack government and military installations in the city.

Kerry's visit came as Kabul desperately tries to bring the insurgent group back to the negotiating table to end their conflict which began in 2001.

Buoyed by a series of victories on the battlefield, the Islamist group have so far refused to talk until their conditions are met, including the departure of 13,000 foreign soldiers from Afghanistan.

"We discussed our shared goal of launching peace talks with the Taleban," Kerry told reporters at a joint press conference with Afghan President Ashraf Ghani in Kabul.

"We call on the Taleban to enter into a peace process, a legitimate process that brings an end to violence," he continued, saying: "Of course there is hope for peace."

Kerry also added that in July, "Nato allies and partners will gather in Warsaw in order to consider the next round of assistance for the Afghan National Defence and Security Forces."

Another meeting is also scheduled this October in Brussels to review development aid to Afghanistan.

Afghanistan, the US, China and Pakistan had formed a four-way group to try to jump-start the talks that were first held in Islamabad last July but fell away after it emerged later that month the Taleban's founder Mullah Omar was dead, leading to infighting within the group.

President Ghani backed Kerry's call, adding: "Peace is the vital need for the nation and the government of Afghanistan and the United States of America - especially you - have always been our partner in creating a peaceful atmosphere and regional stability."

"I would like to thank you for the consistent sacrifices and the support of the United States of America. Thousands of your countrymen, your sons and young Americans have given their lives in Afghanistan," he said.

Kerry's first port of call was Nato headquarters, where he met with General John Nicholson, the newly appointed head of the alliance's Resolute Support mission, and US troops.

The US currently has about 9,800 soldiers in the country who have been officially limited to a training and advisory role since the end of their combat mission in 2014.

Hopes for peace and economic stability were high following the 2014 presidential election, which marked the first democratic transition of power following the departure of Hamid Karzai who had ruled the country for almost a decade.

But 18 months after Afghanistan's present unity government was formed, "there have been challenges both in terms of politics, but also in terms of the resilience... of the Taleban," according to the US special envoy to Pakistan and Afghanistan Richard Olson.

On the political front, parliamentary elections are due to be held Oct 15, more than a year behind schedule, due to deep differences at the highest levels of government between Ghani and Chief Executive Abdullah Abdullah.

Several ministers have resigned in recent months because of the tensions between the two camps.

One of the most high-profile resignations was Ghani's number two, the former interior minister Noor-ul-Haq Ulumi who left office in February. His successor, Taj Mohammad Jahid, was confirmed by parliament on Saturday morning.

Both Ghani and Abdullah claimed victory in the presidential election, leading to a three-month stalemate until a breakthrough deal mediated by Kerry.

The delay in legislative elections is also due to the Taleban's resurgent campaign of violence, which they stepped up following the withdrawal of Nato combat troops in 2014.

New leader Mullah Akhtar Mansour has overseen spectacular military victories, including the brief capture of northern Kunduz city last September.