A Taliban suicide bomber wearing an Afghan army uniform set off a huge explosion Saturday while trying to board a military bus in the capital, killing 30 people, most of them soldiers, officials said. Hours later, the Afghan president offered to meet personally with the Taliban leader for peace talks and give the militants a position in government.

Strengthening a call for negotiations he has made with increasing frequency the last several weeks, President Hamid Karzai said he was willing to meet with Taliban leader Mullah Omar and Gulbuddin Hekmatyar, a former prime minister and factional warlord leader.

"If I find their address, there is no need for them to come to me, I'll personally go there and get in touch with them," Karzai said. "Esteemed Mullah, sir, and esteemed Hekmatyar, sir, why are you destroying the country?"

Karzai said he has contacts with Taliban militants through tribal elders but that there are no direct and open government communication channels with the fighters.

"If a group of Taliban or a number of Taliban come to me and say, 'President, we want a department in this or in that ministry or we want a position as deputy minister ... and we don't want to fight anymore... If there will be a demand and a request like that to me, I will accept it because I want conflicts and fighting to end in Afghanistan," Karzai said.

"I wish there would be a demand as easy as this. I wish that they would want a position in the government. I will give them a position," he said.

Four employees with the International Committee of the Red Cross, kidnapped earlier this week while negotiating the release of a German hostage, were freed in good health Saturday, said Mohabullah, the police director of criminal investigations of the Sayad Abad district where the four were taken. He had no news about the German.

"The unconditional release of our four colleagues is a great relief to us and their families," said Franz Rauchenstein, deputy head of the ICRC delegation in Kabul.

The number of kidnappings in Afghanistan has spiked in recent months after the Taliban secured the release of five insurgent prisoners in exchange for a captive Italian journalist in March — a heavily criticized swap that many feared would encourage abductions.

The Taliban kidnapped 23 South Koreans in July, a hostage crisis that scored the militants face-to-face talks with South Korean government delegates. Two of the Koreans were killed; 21 were eventually released.

Karzai earlier this month renewed a call for talks with the Taliban, and a spokesman for the militant group initially said the fighters might be open to negotiations. But spokesman Qari Yousef Ahmadi later said foreign troops must first leave the country — a demand Karzai said Saturday he would not meet.

"It should be very clear until all our roads are paved, until we have good electricity and good water, and also until we have a better Afghan national army and national police, I don't want any foreigners to leave Afghanistan," he said.

He said he still wanted negotiations with Taliban militants of Afghan origin "for peace and security." He ruled out talks with al-Qaida and other foreign fighters.

NATO and the United Nations have said an increasing number of Taliban fighters are interested in laying down their arms. NATO's ambassador to Afghanistan, Daan Everts, said this month that NATO would look into the possibility of talks.

More than 4,500 fighters have taken part in a two-year reconciliation process, but the Taliban have launched more than 100 suicide attacks this year, a record pace.

Saturday's explosion ripped off the roof of the bus and tore out its sides, leaving a charred hull of burnt metal. It was reminiscent of the deadliest insurgent attack in Afghanistan since the U.S.-led invasion in 2001 — when a bomber boarded a police academy bus at Kabul's busiest transportation hub in June and killed 35 people.

Dozens of civilians and police officers searched for bodies. Police and soldiers climbed trees to retrieve some body parts. Nearby businesses also were damaged.

"For 10 or 15 seconds, it was like an atom bomb — fire, smoke and dust everywhere," said Mohammad Azim, a police officer who witnessed the explosion.

Karzai said 30 people were killed — 28 soldiers and two civilians. The Health Ministry said another 30 were wounded.

"It was a terrible tragedy, no doubt an act of extreme cowardice," Karzai said. "Whoever did this was against people, against humanity, definitely against Islam. A man who calls himself Muslim will not blow up innocent people in the middle of Ramadan," the Muslim holy month.

A purported Taliban spokesman, Zabiullah Mujahid, claimed the militant group was responsible for the blast in a text message to The Associated Press. Mujahid said the bomber was a Kabul resident named Azizullah.

The bus had stopped in front of a movie theater to pick up soldiers when a bomber wearing a military uniform tried to board around 6:45 a.m. local time, army spokesman Gen. Mohammad Zahir Azimi said.

"Typically there are people checking the IDs of soldiers who want to board the bus," Azimi said. "While they were checking the IDs the bomber tried to get on the bus and blew himself up there