Leaders of the world’s 20 leading economies met in the German city of Hamburg Friday to discuss the global economy, climate change and the fight against terrorism.

Chancellor Angela Merkel greeted leaders, including U.S. President Donald Trump, Russian President Vladimir Putin and Turkey's Recep Tayyip Erdogan, before a retreat session on counterterrorism.

Several leaders did not arrive at the G20 summit on time because of widespread protests in the city by anti-capitalist protestors.

While most protestors remained peaceful, several anarchist groups set dozens of cars on fire, local media reported.

Hamburg police have beefed up security, with hundreds of police patrolling the city, and police helicopters circling the summit site.

The G20 leaders are scheduled to discuss global economy, development and trade during a working lunch.

In the afternoon, their discussions are expected to focus on sustainable development, climate change and energy.

Merkel urges compromise

In opening remarks, Chancellor Merkel urged leaders to show compromise at the Hamburg summit to agree a joint declaration and give a united message on addressing global problems.

“I am absolutely certain that each and every one [of us] will do his or her own bit in order to give a good contribution to the success of this meeting,” she said.

“We all know that time is of essence… Solutions can only be found if we are ready to strike a compromise,” she added. 

Export giants Germany and China are pushing for the G20 to endorse free trade and oppose economic isolationism amid growing concerns over President Trump’s protectionist stance.